32 results on '"Hewitt LA"'
Search Results
2. The role of biotransformation–detoxication in acetone-, 2-butanone-, and 2-hexanone-potentiated chloroform-induced hepatotoxicity
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Hewitt La, Valiquette C, and Plaa Gl
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Male ,Cytochrome ,Physiology ,Reactive intermediate ,Mixed Function Oxygenases ,Acetone ,chemistry.chemical_compound ,Biotransformation ,Physiology (medical) ,Animals ,Pharmacology ,Chloroform ,biology ,2-Hexanone ,Proteins ,Rats, Inbred Strains ,General Medicine ,Glutathione ,Ketones ,Monooxygenase ,Butanones ,Rats ,Hexanones ,Liver ,chemistry ,Biochemistry ,Inactivation, Metabolic ,Microsomes, Liver ,biology.protein ,Chemical and Drug Induced Liver Injury - Abstract
The hepatotoxicity of chloroform (CHCl3) is thought to require biotransformation, by the polysubstrate monooxygenase system (P-450), to a reactive intermediate(s). Therefore, the potentiation of CHCl3-induced hepatotoxicity, which occurs following exposure to certain ketones, may hypothetically be explained by a reduced capacity of the cell to form glutathione conjugates (detoxicate the intermediate) and (or) by an increased rate of reactive intermediate(s) generation secondary to a modification of the P-450 system. To test these hypotheses, liver damage, as indicated by elevation in plasma alanine aminotransferase and ornithine carbamyl transferase activities, was modulated in male Sprague-Dawley rats by varying the time interval (10, 18, 24, 48, 72, 96 h) between acetone, 2-butanone, or 2-hexanone (15 mmol/kg, p.o.) pretreatment and CHCl3 (0.5 mL/kg, p.o.) administration. These data were compared with hepatic glutathione and with various parameters of the polysubstrate monooxygenase system: cytochrome P-450, cytochrome c reductase, cytochrome b5, and microsomal binding of 14CHCl3-derived radiolabel. Reduced detoxication capacity does not appear to be involved as hepatic glutathione levels were not reduced. Globally, a relationship between modifications to the polysubstrate monooxygenase system and potentiation of CHCl3-induced hepatotoxicity appears to exist. The rank order of each ketone's ability to modify P-450 parameters was the same in most instances as that based on peak ability to potentiate CHCl3-induced hepatotoxicity: 2-hexanone > 2-butanone ≥ acetone. Therefore, these results suggest that a general relationship exists between the ketone-induced potentiation of CHCl3-induced hepatotoxicity and increased CHCl3 reactive metabolite generation. However, other factors may also contribute to the phenomenon.
- Published
- 1987
3. Fractional hepatic localization of 14CHCl3 in mice and rats treated with chlordecone or mirex
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William R. Hewitt, Hewitt La, and Gabriel L. Plaa
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Male ,medicine.medical_specialty ,Insecticides ,Irreversible binding ,Toxicology ,Fractional distribution ,Mice ,Cytochrome P-450 Enzyme System ,In vivo ,Internal medicine ,medicine ,Distribution (pharmacology) ,Animals ,Liver damage ,Carbon Radioisotopes ,Mirex ,Structural analog ,Chemistry ,Rats, Inbred Strains ,Rats ,Endocrinology ,Biochemistry ,Liver ,Chlordecone ,Enzyme Induction ,Reactive metabolite ,Chloroform - Abstract
In rodents chlordecone, but not mirex, a nonketonic structural analog, significantly augments CHCl3-induced liver damage, at least in part, by increasing CHCl3 bioactivation. To determine whether the fractional distribution of CHCl3 was altered in chlordecone-pretreated animals, the irreversible binding of 14CHCl3 to various liver constituents (a measure of CHCl3 bioactivation) was examined in vivo in mice and rats. Chlordecone, but not mirex, increased both total and irreversibly bound 14CHCl3; furthermore, changes in the 14C localization between lipid, protein and acid-soluble fractions were noted. Thus, the results suggest that differences exist between chlordecone and mirex with respect to their capacity to increase the quantity of CHCl3-derived reactive metabolite and the eventual distribution of reactive metabolite.
- Published
- 1983
4. Temporal relationships between biotransformation, detoxication, and chlordecone potentiation of chloroform-induced hepatotoxicity
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Hewitt La, Caillé G, and Gabriel L. Plaa
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Male ,Insecticides ,Time Factors ,Physiology ,Bilirubin ,Pharmacology ,Mixed Function Oxygenases ,chemistry.chemical_compound ,Cytochrome P-450 Enzyme System ,Physiology (medical) ,Cytochrome b5 ,Animals ,Biotransformation ,Ornithine Carbamoyltransferase ,NADPH-Ferrihemoprotein Reductase ,biology ,Cytochrome P450 ,Alanine Transaminase ,Drug Synergism ,Rats, Inbred Strains ,General Medicine ,Glutathione ,Cytochrome b Group ,Rats ,Kinetics ,Cytochromes b5 ,chemistry ,Biochemistry ,Liver ,Chlordecone ,Toxicity ,biology.protein ,Microsome ,Glucose-6-Phosphatase ,Microsomes, Liver ,Kepone ,Chloroform ,Corn oil - Abstract
Exposure to chlordecone (CD, Kepone) is known to increase the hepatotoxicity of chloroform (CHCl3) in rats. A time-course analysis was conducted relating several indices of biotransformation capacity with the ability of CD to potentiate CHCl3-induced hepatotoxicity. Male Sprague–Dawley rats were given a single administration of corn oil alone or CD (50 mg/kg, po) dissolved in corn oil. At 2, 4, 8, 16, 20, 24, or 32 days posttreatment, groups of rats were killed and their livers were analyzed for (i) cytochrome P-450, NADPH-dependent cytochrome c reductase, cytochrome b5 and glutathione content or (ii) in vitro irreversible binding of 14CHCl3-derived radiolabel to microsomal protein. Similarly treated rats were challenged (2–32 days posttreatment) with CHCl3 (0.5 mL/kg po); 24 h later, liver damage was assessed by plasma alanine aminotransferase (ALT), plasma ornithine carbamyl transferase (OCT), plasma bilirubin, and hepatic glucose-6-phosphatase. CD potentiation was maximal 2 days posttreatment; and enhanced susceptibility to CHCl3 persisted up to 20–24 days post-CD treatment. In a parallel study animals treated with chlordecone were killed 8, 16, 20, 24, or 32 days later. Blood, kidney, liver, and adipose tissue samples were taken and analyzed for chlordecone content. The results suggest that a general temporal correlation exists between biotransformation rate (microsomal 14C binding), chlordecone content, and the severity of liver injury; the other parameters monitored do not appear to relate directly to the potentiation.
- Published
- 1986
5. Durability of the Clinical Benefit of Droxidopa for Neurogenic Orthostatic Hypotension During 12 Weeks of Open-Label Treatment.
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Hauser RA, Favit A, Hewitt LA, Lindsten A, Gorny S, Kymes S, and Isaacson SH
- Abstract
Introduction: Droxidopa is approved to treat neurogenic orthostatic hypotension (nOH) symptoms in patients with autonomic failure based on short-term clinical trial data. Additional data on the long-term efficacy of droxidopa are needed. We have evaluated the 12-week efficacy and tolerability of droxidopa in patients with nOH in an open-label period of an ongoing phase 4 study ., Methods: Patients received 12 weeks of open-label treatment with an individually optimized droxidopa dose (100-600 mg, 3 times daily) as identified during a preceding titration period. Patient-reported outcomes included the Orthostatic Hypotension Symptom Assessment (OHSA), Orthostatic Hypotension Daily Activity Scale (OHDAS), and clinician- and patient-rated Clinical Global Impression-Severity (CGI-S) scales. Supine blood pressure (BP) and adverse events (AEs) were recorded., Results: Data from 114 patients enrolled into the 12-week open-label period were available for analyses. After 12 weeks of droxidopa treatment, patients reported significant (P < 0.0001) improvements from baseline in OHSA and OHDAS composite and individual item scores and on clinician and patient CGI-S scores. Mean ± SD supine systolic and diastolic BP at week 12 increased by 15.5 ± 22.9 and 7.8 ± 11.7 mmHg from baseline, respectively (P < 0.0001 for both). The most frequently reported AEs were falls (17%), headache (13%), and dizziness (9%); one (0.9%) patient reported an AE of supine hypertension., Conclusion: During 12 weeks of open-label treatment, droxidopa was associated with significant improvement from baseline in nOH symptoms and activities of daily living. No clinically important changes in supine hypertension or AEs of concern were observed. These results support the efficacy of droxidopa beyond 2 weeks of treatment., Trial Registration: NCT02586623., (© 2022. The Author(s).)
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- 2022
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6. Psychometric validation of a patient-reported single-item assessment of 'Good Day Bad Day' in a neurogenic orthostatic hypotension population treated with droxidopa.
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François C, Germain N, Majewska R, Taieb V, Hewitt LA, and Kymes S
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Background: Symptoms of neurogenic orthostatic hypotension (nOH), including lightheadedness/dizziness, presyncope, syncope, and falls, can lead to impaired functional ability and reduced quality of life. Because the severity and frequency of nOH symptoms fluctuate, it may be difficult for patients to accurately quantify the effect of symptoms on their daily lives using available outcome measures. A new single-item instrument, the 'Good Day Bad Day,' was developed, and its psychometric validity was assessed in patients with nOH., Methods: Data from a 6-month, prospective, observational cohort study of patients with nOH who were newly initiating droxidopa treatment were used. Patients were asked to quantify the number of good and bad days in the previous 7 days and responded to other validated patient-reported outcomes instruments. The concurrent and discriminant validities and the stability of the Good Day Bad Day instrument were assessed., Results: A total of 153 patients were included in the analysis (mean [SD] age, 62.3 [17] years). Change in the number of good days moderately correlated with improvements in other patient-reported outcomes (rho value range, -0.38 to -0.61). When data were examined categorically (low vs high symptom severity), the mean number of good days was higher in subgroups representing low symptom severity across measures at 1, 3, and 6 months (all P ≤ 0.01)., Conclusions: The Good Day Bad Day instrument provided good discrimination at baseline and over time and may aid in assessment of the effects of nOH symptoms on patients., Competing Interests: CF is an employee of Creativ-Ceutical, was formerly employed by Lundbeck, and is a shareholder of Lundbeck. RM is an employee of Creativ-Ceutical, and NG and VT were employees of Creativ-Ceutical at the time of the validation analyses. LAH and SK are employees of Lundbeck. This work was supported by Lundbeck; the data reported were derived from a study that was supported by Lundbeck. The sponsor participated in the design of this study, data analysis and interpretation, and in the preparation of the manuscript., (© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)
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- 2022
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7. Characterization of the changes in supine blood pressure with long-term use of droxidopa in patients with neurogenic orthostatic hypotension.
- Author
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Hewitt LA, Lindsten A, Gorny S, Karnik-Henry M, Kymes S, and Favit A
- Abstract
Background and Aims: Patients with neurogenic orthostatic hypotension (nOH) due to autonomic dysfunction may also experience supine hypertension (defined as supine systolic blood pressure [SBP] ≥140 mmHg). Because pressor agents used to improve nOH symptoms by increasing standing blood pressure (BP) may exacerbate or cause supine hypertension, changes in supine BP with nOH treatments are of interest., Methods: This post hoc study examined changes in SBP in patients receiving droxidopa (100-600 mg, three times daily) during a 12-month long-term extension study based on whether patients had supine hypertension (ie, supine SBP ≥140 mmHg) at baseline. Shifts from baseline in supine hypertension categorization and mean supine and standing SBP after 6 and 12 months of treatment with droxidopa were determined., Results: At baseline, 64 patients did not have supine hypertension (mean supine SBP, 120 mmHg) and 38 patients had supine hypertension (mean supine SBP, 157 mmHg). A similar percentage of patients shifted from their respective baseline supine hypertension categorization (ie, with or without supine hypertension) to the other category after receiving droxidopa for 6 or 12 months. After 12 months of droxidopa treatment, patients with supine hypertension at baseline had a mean supine SBP decrease of 3 mmHg and a mean standing SBP increase of 9 mmHg. Patients without supine hypertension at baseline had mean supine and standing SBP increases of 12 and 15 mmHg, respectively., Conclusions: There was no consistent or progressive elevation in supine SBP over time during the 12-month treatment with droxidopa in patients either with or without supine hypertension at baseline. These data suggest that long-term droxidopa treatment for nOH does not adversely affect supine BP., Competing Interests: All authors are employees of Lundbeck., (© 2021 The Authors. Health Science Reports published by Wiley Periodicals LLC.)
- Published
- 2021
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8. A Call to Action: The Role of Healthcare Providers in Reducing the Burden Associated with Neurogenic Orthostatic Hypotension.
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Gibson JS, Hunter CB, and Hewitt LA
- Abstract
Neurogenic orthostatic hypotension (nOH) is a sustained fall in blood pressure upon standing that frequently affects patients with neurodegenerative diseases (e.g., Parkinson disease) and manifests with symptoms such as lightheadedness and dizziness upon standing. nOH can severely affect patients by increasing the risk of falls and injuries and by decreasing functionality, independence, and quality of life. However, the condition is often under-recognized because of many factors, including the nonspecific nature of the symptoms, patient comorbidities, and patients' reluctance to discuss their symptoms with their healthcare providers. Increased awareness of the burden of nOH and recognition of potential barriers to efficient diagnosis may lead to improved clinical outcomes and better quality of life for patients. To better understand the manifestations and real-life impact of living with nOH symptoms, perspectives from a patient with nOH and his caregiver (wife) are provided, along with key findings from a published survey of patients and caregivers on the burden of nOH. In addition, insights and advice on a practical approach for diagnosing, educating, and treating patients with nOH are outlined.
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- 2020
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9. Use of droxidopa for the long-term treatment of neurogenic orthostatic hypotension.
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Raj SR and Hewitt LA
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- 2019
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10. Integrated Analysis of Droxidopa for the Treatment of Neurogenic Orthostatic Hypotension in Patients with Parkinson Disease.
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Hauser RA, Biaggioni I, Hewitt LA, and Vernino S
- Abstract
Introduction: Neurogenic orthostatic hypotension (nOH) is associated with neurodegenerative conditions, may cause symptoms of end-organ hypoperfusion, increases fall risk, and can negatively impact quality of life. Droxidopa is approved for the treatment of symptomatic nOH in adults. As the largest subpopulation of patients with nOH has a diagnosis of Parkinson disease (PD), the efficacy and tolerability of droxidopa in patients with PD and nOH were examined using integrated clinical trial data., Methods: Post hoc analyses included data from the phase 3, randomized, placebo-controlled clinical trials of droxidopa (two short-term [1-2 weeks] trials and one medium-term [8-10 weeks] trial) in the subset of participants with PD and symptomatic nOH. Efficacy was assessed using standing blood pressure (BP) measurements and the Orthostatic Hypotension Questionnaire (OHQ), a patient-reported evaluation of nOH symptoms (Orthostatic Hypotension Symptom Assessment [OHSA]), and their impact (Orthostatic Hypotension Daily Activity Scale [OHDAS])., Results: The analysis included 307 patients with PD (droxidopa, n = 150; placebo, n = 157). Compared with placebo, droxidopa significantly improved the OHQ composite score ( P = 0.014), the OHSA composite score ( P = 0.022), and the OHDAS composite score ( P = 0.029) from baseline to end of study/week one. We found significant increases in standing mean systolic/diastolic BP for droxidopa versus placebo ( P = 0.003/0.002). Adverse event (AE) rates were qualitatively similar between groups; the most frequently reported AEs in the droxidopa groups included headache, dizziness, nausea, and hypertension., Conclusions: These post hoc analyses suggest that droxidopa provides meaningful clinical benefits and is well tolerated in the treatment of symptomatic nOH in patients with PD.
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- 2018
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11. Characterization of the symptoms of neurogenic orthostatic hypotension and their impact from a survey of patients and caregivers.
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Claassen DO, Adler CH, Hewitt LA, and Gibbons C
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- Adult, Humans, Parkinson Disease complications, Quality of Life, Caregivers statistics & numerical data, Hypotension, Orthostatic diagnosis, Hypotension, Orthostatic epidemiology, Hypotension, Orthostatic etiology, Hypotension, Orthostatic physiopathology
- Abstract
Background: Neurogenic orthostatic hypotension (nOH) results from impaired vasoconstriction due to dysfunction of the autonomic nervous system and is commonly associated with Parkinson disease (PD), multiple system atrophy (MSA), and pure autonomic failure. nOH can increase the risk of falls due to symptoms that include postural lightheadedness or dizziness, presyncope, and syncope. The purpose of this study was to obtain information from patients and caregivers regarding the symptoms and burden of nOH to expand on limited knowledge regarding the impact of nOH on quality of life., Methods: This author-designed survey included questions regarding nOH (e.g., frequency and impact of symptoms, management) and was conducted online by Harris Poll via distribution to individuals who agreed to participate in Harris Poll online surveys or who were members of relevant disease advocacy organizations. Eligible patients were aged ≥ 18 years with PD, MSA, or pure autonomic failure and ≥ 1 of the following: orthostatic hypotension (OH), nOH, low blood pressure upon standing, or OH/nOH symptoms. Eligible caregivers cared for such patients but were not necessarily linked to any patient participant., Results: Survey responses were received from 363 patients and 128 caregivers. PD was the most frequent underlying disorder (90% of patients; 88% of individuals managed by the caregivers). Despite meeting survey diagnosis criteria, a formal diagnosis of OH or nOH was reported by only 36% of patients and 16% of caregivers. The most frequent symptoms of nOH were dizziness or lightheadedness, fatigue when standing, and difficulty walking. A negative impact on patient quality of life caused by nOH symptoms was reported by 59% of patients and 75% of caregivers. Most respondents (≥87%) reported that nOH symptoms adversely affected patients' ability to perform everyday activities (most frequently physical activity/exercise, housework, and traveling). Falls (≥1) in the previous year due to nOH symptoms were reported by 57% of patients and 80% of caregivers., Conclusions: These survey results support the premise that nOH symptoms have a substantial negative impact on patient function and quality of life. The relatively low rates of formal nOH/OH diagnosis suggest the need for heightened awareness regarding the condition and its symptom burden.
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- 2018
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12. Comparison of the Pharmacokinetics of Droxidopa After Dosing in the Fed Versus Fasted State and with 3-Times-Daily Dosing in Healthy Elderly Subjects.
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Chen JJ and Hewitt LA
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- Administration, Oral, Aged, Antiparkinson Agents blood, Antiparkinson Agents pharmacokinetics, Biological Availability, Cross-Over Studies, Droxidopa blood, Female, Healthy Volunteers, Humans, Male, Droxidopa pharmacokinetics, Fasting, Food-Drug Interactions
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Background: Droxidopa is an oral prodrug of norepinephrine approved for the treatment of symptomatic neurogenic orthostatic hypotension. This two-part, randomized, crossover study evaluated the 24-h pharmacokinetic profile of droxidopa in 24 healthy elderly subjects., Methods: Noncompartmental analysis was used to calculate the area under the plasma concentration-time curve (AUC), maximum plasma concentration (C
max ), time of Cmax (tmax ), and elimination half-life (t½e ) of droxidopa and metabolites. Droxidopa was administered in the fed (high-fat/high-calorie meal) or fasted state either as a single 300-mg dose (three 100-mg capsules) or 3 times/day (TID) (three 100-mg capsules) at 4-h intervals., Results: Administration of a single droxidopa dose in the fed versus fasted state decreased mean Cmax (2057 vs 3160 ng/mL) and mean AUC (10,927 vs 13,857 h × ng/mL) and increased median tmax twofold (4.00 vs 2.00 h). Differences between the fed and fasted state for mean t½e (2.58 vs 2.68 h) were not observed. Fed versus fasted geometric mean ratios for Cmax and AUC were 66% [90% confidence interval (CI) 60.7-71.7] and 80% (90% CI 72.6-88.1), respectively. With TID dosing, similar values for Cmax were observed after each dose (range 2789-3389 ng/mL) with no return to baseline between doses. Norepinephrine Cmax was 895 pg/mL following dose 1, with no further increases upon subsequent doses; norepinephrine levels remained above baseline for 12-16 h after dose 1., Conclusions: Absorption of a single dose of droxidopa is slowed after a high-fat/high-calorie meal; for consistent effect, administer droxidopa in the same manner (with or without food). Pharmacokinetic parameters of droxidopa are similar after single and TID dosing. ClinicalTrials.gov Identifier: NCT01149629.- Published
- 2018
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13. Impact of the Norepinephrine Prodrug Droxidopa on the QTc Interval in Healthy Individuals.
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White WB, Hewitt LA, and Mehdirad AA
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- Adult, Cross-Over Studies, Double-Blind Method, Electrocardiography methods, Female, Healthy Volunteers, Heart Rate physiology, Humans, Male, Middle Aged, Young Adult, Antiparkinson Agents pharmacology, Droxidopa pharmacology, Electrocardiography drug effects, Heart Rate drug effects, Norepinephrine pharmacology, Prodrugs pharmacology
- Abstract
A double-blind, 4-period crossover study (NCT01327066) was conducted to assess the effect of the novel norepinephrine prodrug droxidopa on the QT interval in in healthy subjects. Subjects were randomized to receive a single dose of droxidopa 600 mg (maximal dose) and 2000 mg (supratherapeutic dose) compared with the positive control, moxifloxacin 400 mg, and placebo, each separated by a 3-day washout period. Patients were monitored by continuous Holter monitoring, and electrocardiograms (ECGs) were extracted 0.5-23 hours after dosing. Blood samples for pharmacokinetic analysis were collected before dosing and after ECG data collection. The primary end point was the time-matched placebo-adjusted change from baseline in the individually corrected QT (QTcI). The time-averaged QTcI mean placebo-corrected changes from baseline for droxidopa 600 and 2000 mg were 0.1 milliseconds (90%CI, -0.9 to 1.0 milliseconds) and 0.3 milliseconds (90%CI, -0.6 to 1.3 milliseconds), respectively, and 9 milliseconds (90%CI, 8.4-10.3 milliseconds) for moxifloxacin. This study found no effect of either dose of droxidopa on cardiac repolarization using QTcI. Analysis of the pharmacokinetic/pharmacodynamic relationship and cardiac repolarization showed no association with droxidopa exposure. There were no clinically relevant effects of droxidopa on heart rate, atrioventricular conduction, or cardiac depolarization identified. No morphologic ECG changes were observed., (© 2017 The Authors. Clinical Pharmacology in Drug Development Published by Wiley Periodicals, Inc. on behalf of American College of Clinical Pharmacology.)
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- 2018
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14. Cardiovascular Safety of Droxidopa in Patients With Symptomatic Neurogenic Orthostatic Hypotension.
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White WB, Hauser RA, Rowse GJ, Ziemann A, and Hewitt LA
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- Humans, Hypotension, Orthostatic complications, Randomized Controlled Trials as Topic, Treatment Outcome, Antiparkinson Agents therapeutic use, Cardiovascular Diseases complications, Droxidopa therapeutic use, Hypotension, Orthostatic drug therapy
- Abstract
The norepinephrine prodrug droxidopa improves symptoms of neurogenic orthostatic hypotension, a condition that is associated with diseases of neurogenic autonomic failure (e.g., Parkinson disease, multiple system atrophy, pure autonomic failure). These conditions are more prevalent in older patients who also have cardiovascular co-morbidities. Hence, we evaluated the cardiovascular safety of droxidopa in patients with symptomatic neurogenic orthostatic hypotension who participated in randomized controlled studies (short-term studies of 1 to 2 weeks and an intermediate 8- to 10-week study) and long-term open-label studies. Rates of cardiovascular adverse events (AEs) for patients treated with droxidopa were 4.4% in the intermediate study and 10.8% in the long-term open-label studies. Adjusting for exposure time, cardiovascular AE rates were 0.30 events/patient-year in the short-term and intermediate studies and 0.15 events/patient-year in the long-term open-label studies. The incidence of treatment discontinuation due to blood pressure-related events was approximately 2.5%. Among patients with a history of cardiac disorders at baseline, the rates of cardiovascular-related and blood pressure-related AEs were nominally higher with droxidopa compared to placebo. Most of these events were minor atrial arrhythmias; none were major adverse cardiovascular events or deaths. In conclusion, small increases in cardiovascular AEs were observed with droxidopa compared to placebo; this was most evident in patients with preexisting cardiac disorders., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2017
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15. Effects of the novel norepinephrine prodrug, droxidopa, on ambulatory blood pressure in patients with neurogenic orthostatic hypotension.
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Kaufmann H, Norcliffe-Kaufmann L, Hewitt LA, Rowse GJ, and White WB
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- Aged, Aged, 80 and over, Blood Pressure Monitoring, Ambulatory, Circadian Rhythm physiology, Droxidopa, Female, Humans, Hypertension chemically induced, Male, Middle Aged, Norepinephrine administration & dosage, Norepinephrine adverse effects, Prodrugs administration & dosage, Prodrugs adverse effects, Vasoconstrictor Agents administration & dosage, Vasoconstrictor Agents adverse effects, Blood Pressure drug effects, Hypotension, Orthostatic drug therapy, Norepinephrine therapeutic use, Prodrugs therapeutic use, Vasoconstrictor Agents therapeutic use
- Abstract
The prodrug droxidopa increases blood pressure (BP) in patients with neurogenic orthostatic hypotension. The BP profile of droxidopa in neurogenic orthostatic hypotension patients (n = 18) was investigated using ambulatory BP monitoring. Following dose optimization and a washout period, 24-hour "off-drug" data were collected. "On-drug" assessment was conducted after 4-5 weeks of droxidopa treatment (mean dose, 444 mg, three times daily). Ambulatory monitoring off drug revealed that 90% of patients already had abnormalities in the circadian BP profile and did not meet criteria for normal nocturnal BP dipping. On treatment, both overall mean 24-hour systolic and diastolic BPs were higher compared to off drug (137/81 mm Hg vs. 129/76 mm Hg; P = .017/.002). Mean daytime systolic BP was significantly higher with droxidopa (8.4 ± 3.1 mm Hg; P = .014). Although nocturnal BP was not significantly higher on droxidopa versus off treatment (P = .122), increases in nocturnal (supine) BP ≥10 mm Hg were observed in four cases (22%). Severe supine systolic hypertensive readings at night (>200 mm Hg) were captured in one case and only while on treatment. These data demonstrate that ambulatory BP monitoring is useful to evaluate the circadian BP profile after initiating treatment with a pressor agent., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
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16. Droxidopa and Reduced Falls in a Trial of Parkinson Disease Patients With Neurogenic Orthostatic Hypotension.
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Hauser RA, Heritier S, Rowse GJ, Hewitt LA, and Isaacson SH
- Subjects
- Adult, Aged, Aged, 80 and over, Double-Blind Method, Female, Humans, Male, Middle Aged, Severity of Illness Index, Accidental Falls, Antiparkinson Agents therapeutic use, Droxidopa therapeutic use, Hypotension, Orthostatic complications, Parkinson Disease complications, Parkinson Disease drug therapy
- Abstract
Objectives: Droxidopa is a prodrug of norepinephrine indicated for the treatment of orthostatic dizziness, lightheadedness, or the "feeling that you are about to black out" in adult patients with symptomatic neurogenic orthostatic hypotension caused by primary autonomic failure including Parkinson disease (PD). The objective of this study was to compare fall rates in PD patients with symptomatic neurogenic orthostatic hypotension randomized to droxidopa or placebo., Methods: Study NOH306 was a 10-week, phase 3, randomized, placebo-controlled, double-blind trial of droxidopa in PD patients with symptomatic neurogenic orthostatic hypotension that included assessments of falls as a key secondary end point. In this report, the principal analysis consisted of a comparison of the rate of patient-reported falls from randomization to end of study in droxidopa versus placebo groups., Results: A total of 225 patients were randomized; 222 patients were included in the safety analyses, and 197 patients provided efficacy data and were included in the falls analyses. The 92 droxidopa patients reported 308 falls, and the 105 placebo patients reported 908 falls. In the droxidopa group, the fall rate was 0.4 falls per patient-week; in the placebo group, the rate was 1.05 falls per patient-week (prespecified Wilcoxon rank sum P = 0.704; post hoc Poisson-inverse Gaussian test P = 0.014), yielding a relative risk reduction of 77% using the Poisson-inverse Gaussian model. Fall-related injuries occurred in 16.7% of droxidopa-treated patients and 26.9% of placebo-treated patients., Conclusions: Treatment with droxidopa appears to reduce falls in PD patients with symptomatic neurogenic orthostatic hypotension, but this finding must be confirmed., Competing Interests: and Source of Funding: The trial and post hoc analyses were funded by Lundbeck. R.A.H. has received honoraria or payments for consulting, advisory services, or speaking services from Chelsea Therapeutics (now Lundbeck NA Ltd) and Lundbeck. L.A.H. is an employee of Lundbeck. G.J.R. was an employee of Lundbeck at the time of the studies and manuscript development. S.H. has provided consulting services to Lundbeck NA Ltd. S.H.I. has received honoraria in the past 12 months for continuing medical education, consultancy services, research grants, and/or promotional speaking from Lundbeck. The authors received editorial assistance from CHC Group (North Wales, PA), which was supported by Lundbeck LLC.
- Published
- 2016
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17. Analysis of number needed to treat for droxidopa in patients with symptomatic neurogenic orthostatic hypotension.
- Author
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François C, Rowse GJ, Hewitt LA, Vo P, and Hauser RA
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- Aged, Aged, 80 and over, Antiparkinson Agents adverse effects, Droxidopa adverse effects, Female, Humans, Hypotension, Orthostatic etiology, Male, Middle Aged, Outcome Assessment, Health Care methods, Antiparkinson Agents pharmacology, Droxidopa pharmacology, Hypotension, Orthostatic drug therapy, Nervous System Diseases complications, Outcome Assessment, Health Care statistics & numerical data, Randomized Controlled Trials as Topic statistics & numerical data
- Abstract
Background: Droxidopa is an orally active prodrug that significantly improved dizziness/lightheadedness measured using the Orthostatic Hypotension Symptom Assessment (OHSA) Item 1 in patients with neurogenic orthostatic hypotension (nOH) caused by primary autonomic failure (Parkinson disease, multiple system atrophy, and pure autonomic failure), dopamine β-hydroxylase deficiency, or nondiabetic autonomic neuropathy. The efficacy and safety of droxidopa were assessed by determining the number needed to treat (NNT) and the number needed to harm (NNH)., Methods: Data collected in randomized, placebo-controlled clinical studies in adults with a clinical diagnosis of symptomatic nOH were pooled for efficacy and safety analyses. NNT and NNH were calculated as reciprocals of the risk difference (difference in event rates) for droxidopa versus placebo., Results: The NNT for droxidopa for improvement in OHSA Item 1 was <10. The NNH for adverse events (AEs) leading to discontinuation in the pooled studies was 81. The likelihood of being helped or harmed (LHH) calculated from pooled analysis of the NNT for ≥2 units of improvement in OHSA Item 1 score and the NNH for discontinuations due to AEs were 7.8, 8.8, 3.1, and 3.5 for weeks 1, 2, 4, and 8 after randomization, respectively., Conclusions: Droxidopa is efficacious for treatment of nOH, with an NNT below 10 and an acceptable tolerability profile with NNH ranging from 23 to 302 in the pooled analysis of frequently occurring AEs. Based on the LHH for the pooled analysis at week 1, droxidopa is 7.8 times more likely than placebo to show a clinical benefit than result in discontinuation because of an AE., Trial Registrations: ClinicalTrials.gov identifiers: NCT00782340 , first received October 29, 2008; NCT00633880 , first received March 5, 2008; and NCT01176240 , first received July 30, 2010.
- Published
- 2016
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18. Cost-effectiveness of droxidopa in patients with neurogenic orthostatic hypotension: post-hoc economic analysis of Phase 3 clinical trial data.
- Author
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François C, Hauser RA, Aballéa S, Dorey J, Kharitonova E, and Hewitt LA
- Subjects
- Accidental Falls economics, Aged, Blood Pressure, Cost-Benefit Analysis, Dose-Response Relationship, Drug, Double-Blind Method, Female, Humans, Hypotension, Orthostatic etiology, Male, Markov Chains, Parkinson Disease complications, Quality-Adjusted Life Years, Antiparkinson Agents economics, Antiparkinson Agents therapeutic use, Droxidopa economics, Droxidopa therapeutic use, Hypotension, Orthostatic drug therapy
- Abstract
Objective: Falls are associated with neurogenic orthostatic hypotension (nOH) and are an economic burden on the US healthcare system. Droxidopa is approved by the US FDA to treat symptomatic nOH. This study estimates the cost-effectiveness of droxidopa vs standard of care from a US payer perspective., Methods: A Markov model was used to predict numbers of falls and treatment responses using data from a randomized, double-blind trial of patients with Parkinson's disease and nOH who received optimized droxidopa therapy or placebo for 8 weeks. The severity of falls, utility values, and injury-related costs were derived from published studies. Model outcomes included number of falls, number of quality-adjusted life-years (QALYs), and direct costs. Incremental cost-effectiveness ratios (ICERs) were calculated. Outcomes were extrapolated over 12 months., Results: Patients receiving droxidopa had fewer falls compared with those receiving standard of care and gained 0.33 QALYs/patient. Estimated droxidopa costs were $30,112, with estimated cost savings resulting from fall avoidance of $14,574 over 12 months. Droxidopa was cost-effective vs standard of care, with ICERs of $47,001/QALY gained, $24,866 per avoided fall with moderate/major injury, and $1559 per avoided fall with no/minor injury. The main drivers were fall probabilities and fear of fall-related inputs., Limitations: A limitation of the current study is the reliance on falls data from a randomized controlled trial where the placebo group served as the proxy for standard of care. Data from a larger patient population, reflecting 'real-life' patient use and/or comparison with other agents used to treat nOH, would have been a useful complement, but these data were not available., Conclusion: Using Markov modeling, droxidopa appears to be a cost-effective option compared with standard of care in US clinical practice for the treatment of nOH.
- Published
- 2016
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19. Droxidopa for the short-term treatment of symptomatic neurogenic orthostatic hypotension in Parkinson's disease (nOH306B).
- Author
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Hauser RA, Isaacson S, Lisk JP, Hewitt LA, and Rowse G
- Subjects
- Adult, Aged, Aged, 80 and over, Analysis of Variance, Blood Pressure drug effects, Double-Blind Method, Female, Follow-Up Studies, Humans, Hypotension, Orthostatic complications, Male, Middle Aged, Parkinson Disease drug therapy, Surveys and Questionnaires, Treatment Outcome, Antiparkinson Agents therapeutic use, Droxidopa therapeutic use, Hypotension, Orthostatic drug therapy, Parkinson Disease complications
- Abstract
Neurogenic orthostatic hypotension (nOH) results from failure of norepinephrine responses to postural change to maintain standing systolic blood pressure (s-SBP). Droxidopa is an oral prodrug of norepinephrine. Study nOH306 enrolled patients with Parkinson's disease (PD) and symptomatic nOH. Subjects underwent up to 2 weeks of double-blind titration of droxidopa or placebo, followed by 8 weeks of double-blind maintenance treatment (100-600 mg thrice-daily). For the initial 51 subjects (study nOH306A, previously reported), the primary efficacy measure, Orthostatic Hypotension Questionnaire (OHQ) composite score, did not demonstrate significant change versus placebo at maintenance week 8. For the subsequent 171 subjects (study nOH306B, reported here), the primary efficacy measure was change versus placebo on item 1 ("dizziness, lightheadedness, feeling faint, or feeling like you might black out") of the Orthostatic Hypotension Symptom Assessment (OHSA) subsection of the OHQ at maintenance week 1. At week 1, mean (standard deviation) improvement on OHSA item 1 was 2.3 (2.95) for droxidopa versus 1.3 (3.16) for placebo (P = 0.018). In addition, mean increase in s-SBP at week 1 was 6.4 (18.85) for droxidopa versus 0.7 (20.18) mmHg for placebo (nominal P value: 0.032). Differences in change in OHSA item 1 scores from baseline to maintenance weeks 2, 4, and 8 were not statistically significant. Adverse-event (AE) incidence was similar across groups, but 12.4% of droxidopa and 6.1% of placebo subjects withdrew because of AEs. The most common AEs on droxidopa (vs. placebo) were headache (13.5% vs. 7.3%) and dizziness (10.1% vs. 4.9%). Study nOH306B demonstrated subjective (OHSA item 1) and objective (s-SBP) evidence of short-term droxidopa efficacy (vs. placebo) for symptomatic nOH in PD., (© 2014 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.)
- Published
- 2015
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20. A randomized, placebo-controlled, phase 2 study of the efficacy and safety of droxidopa in patients with intradialytic hypotension.
- Author
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Vannorsdall MD, Hariachar S, and Hewitt LA
- Subjects
- Adult, Aged, Antiparkinson Agents, Double-Blind Method, Droxidopa administration & dosage, Female, Humans, Hypotension epidemiology, Kidney Failure, Chronic epidemiology, Kidney Failure, Chronic therapy, Male, Middle Aged, Droxidopa therapeutic use, Hypotension drug therapy, Renal Dialysis adverse effects
- Abstract
Introduction: Intradialytic hypotension (IDH) is the most common complication of hemodialysis (HD), and it plays a significant role in the morbidity and mortality associated with maintenance HD., Methods: This was a placebo-controlled, parallel-group study evaluating efficacy and safety of droxidopa in improving intradialytic blood pressure (BP) responses in 85 adults with end-stage renal disease (ESRD) and prone to IDH. Following screening and baseline periods, patients received 400 mg or 600 mg droxidopa, or placebo, orally 1 hour before HD for 4 weeks. Primary outcome endpoint was the change between baseline and last 2 treatment weeks in average mean arterial pressure (MAP) during HD. Also assessed were changes from baseline in systolic BP (SBP) and diastolic BP (DBP) during and after HD; number of hypotension-induced interventions and symptoms; and adverse events., Results: Increase in droxidopa intra-HD MAP were not significantly different from placebo, although droxidopa groups showed significant improvements in mean SBP after HD of +4.8 ± 11.6 mm Hg (600-mg) and +3.4 ± 13.1 (400-mg) compared with -4.4 ± 17.9 mm Hg in placebo, and the drop seen in mean nadir SBP pre- to intra-HD was also reduced. Changes in mean DBP pre- and post-HD, changes in mean nadir SBP post-HD, or intra-HD SBP were not significant over the treatment period. HD terminations decreased 5-fold in the 600-mg group and 2-fold in the 400-mg group, whereas the number of discontinuations stayed unchanged in the placebo group. Overall, treatment with 600-mg or 400-mg droxidopa was well tolerated in this population., Conclusion: These data suggest that droxidopa may have a role in reducing IDH complications in patients with ESRD on chronic HD.
- Published
- 2015
- Full Text
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21. Randomized withdrawal study of patients with symptomatic neurogenic orthostatic hypotension responsive to droxidopa.
- Author
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Biaggioni I, Freeman R, Mathias CJ, Low P, Hewitt LA, and Kaufmann H
- Subjects
- Adult, Aged, Aged, 80 and over, Antiparkinson Agents administration & dosage, Dose-Response Relationship, Drug, Double-Blind Method, Drug Administration Schedule, Female, Follow-Up Studies, Humans, Hypotension, Orthostatic physiopathology, Male, Middle Aged, Surveys and Questionnaires, Treatment Outcome, Young Adult, Blood Pressure drug effects, Droxidopa administration & dosage, Hypotension, Orthostatic drug therapy, Posture physiology
- Abstract
Unlabelled: We evaluated whether droxidopa, a prodrug converted to norepinephrine, is beneficial in the treatment of symptomatic neurogenic orthostatic hypotension, which results from failure to generate an appropriate norepinephrine response to postural challenge. Patients with symptomatic neurogenic orthostatic hypotension and Parkinson disease, multiple system atrophy, pure autonomic failure, or nondiabetic autonomic neuropathy underwent open-label droxidopa titration (100-600 mg, 3× daily). Responders then received an additional 7-day open-label treatment at their individualized dose. Patients were subsequently randomized to continue with droxidopa or withdraw to placebo for 14 days. We then assessed patient-reported scores on the Orthostatic Hypotension Questionnaire and blood pressure measurements. Mean worsening of Orthostatic Hypotension Questionnaire dizziness/lightheadedness score from randomization to end of study (the primary outcome; N=101) was 1.9±3.2 with placebo and 1.3±2.8 units with droxidopa (P=0.509). Four of the other 5 Orthostatic Hypotension Questionnaire symptom scores and all 4 symptom-impact scores favored droxidopa, with statistical significance for the patient's self-reported ability to perform activities requiring standing a short time (P=0.033) and standing a long time (P=0.028). Furthermore, a post hoc analysis of a predefined composite score of all symptoms (Orthostatic Hypotension Questionnaire composite) demonstrated a significant benefit for droxidopa (P=0.013). There was no significant difference between groups for standing systolic blood pressure (P=0.680). Droxidopa was well tolerated. In summary, this randomized withdrawal droxidopa study failed to meet its primary efficacy end point. Additional clinical trials are needed to confirm that droxidopa is beneficial in symptomatic neurogenic orthostatic hypotension, as suggested by the positive secondary outcomes of this trial., Clinical Trial Registration Url: http://www.clinicaltrials.gov. Unique identifier: NCT00633880., (© 2014 The Authors. Published on behalf of the American Heart Association, Inc., by Wolters Kluwer.)
- Published
- 2015
- Full Text
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22. Droxidopa for neurogenic orthostatic hypotension: a randomized, placebo-controlled, phase 3 trial.
- Author
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Kaufmann H, Freeman R, Biaggioni I, Low P, Pedder S, Hewitt LA, Mauney J, Feirtag M, and Mathias CJ
- Subjects
- Aged, Autonomic Agents administration & dosage, Autonomic Agents adverse effects, Autonomic Nervous System Diseases complications, Autonomic Nervous System Diseases drug therapy, Blood Pressure drug effects, Dizziness drug therapy, Double-Blind Method, Droxidopa administration & dosage, Droxidopa adverse effects, Female, Humans, Male, Middle Aged, Multiple System Atrophy complications, Multiple System Atrophy drug therapy, Nervous System Diseases drug therapy, Parkinson Disease complications, Parkinson Disease drug therapy, Posture, Pure Autonomic Failure complications, Pure Autonomic Failure drug therapy, Time Factors, Treatment Outcome, Autonomic Agents therapeutic use, Droxidopa therapeutic use, Hypotension, Orthostatic drug therapy, Hypotension, Orthostatic etiology, Nervous System Diseases complications
- Abstract
Objective: To determine whether droxidopa, an oral norepinephrine precursor, improves symptomatic neurogenic orthostatic hypotension (nOH)., Methods: Patients with symptomatic nOH due to Parkinson disease, multiple system atrophy, pure autonomic failure, or nondiabetic autonomic neuropathy underwent open-label droxidopa dose optimization (100-600 mg 3 times daily), followed, in responders, by 7-day washout and then a 7-day double-blind trial of droxidopa vs placebo. Outcome measures included patient self-ratings on the Orthostatic Hypotension Questionnaire (OHQ), a validated, nOH-specific tool that assesses symptom severity and symptom impact on daily activities., Results: From randomization to endpoint (n = 162), improvement in mean OHQ composite score favored droxidopa over placebo by 0.90 units (p = 0.003). Improvement in OHQ symptom subscore favored droxidopa by 0.73 units (p = 0.010), with maximum change in "dizziness/lightheadedness." Improvement in symptom-impact subscore favored droxidopa by 1.06 units (p = 0.003), with maximum change for "standing a long time." Mean standing systolic blood pressure (BP) increased by 11.2 vs 3.9 mm Hg (p < 0.001), and mean supine systolic BP by 7.6 vs 0.8 mm Hg (p < 0.001). At endpoint, supine systolic BP >180 mm Hg was observed in 4.9% of droxidopa and 2.5% of placebo recipients. Adverse events reported in ≥ 3% of double-blind droxidopa recipients were headache (7.4%) and dizziness (3.7%). No patients discontinued double-blind treatment because of adverse events., Conclusions: In patients with symptomatic nOH, droxidopa improved symptoms and symptom impact on daily activities, with an associated increase in standing systolic BP, and was generally well tolerated., Classification of Evidence: This study provides Class I evidence that in patients with symptomatic nOH who respond to open-label droxidopa, droxidopa improves subjective and objective manifestation of nOH at 7 days., (© 2014 American Academy of Neurology.)
- Published
- 2014
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23. Droxidopa in patients with neurogenic orthostatic hypotension associated with Parkinson's disease (NOH306A).
- Author
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Hauser RA, Hewitt LA, and Isaacson S
- Subjects
- Aged, Aged, 80 and over, Female, Humans, Hypotension, Orthostatic complications, Male, Middle Aged, Antiparkinson Agents therapeutic use, Droxidopa therapeutic use, Hypotension, Orthostatic drug therapy, Parkinson Disease complications
- Abstract
Background: Neurogenic orthostatic hypotension (nOH) is common in Parkinson's disease (PD), and represents a failure to generate norepinephrine responses appropriate for postural change. Droxidopa (L-threo-3,4-dihydroxyphenylserine) is an oral norepinephrine prodrug., Objective: Interim analyses of the initial patients enrolled in a multicenter, randomized, double-blind, placebo-controlled phase 3 trial of droxidopa for nOH in PD (ClinicalTrials.gov Identifier: NCT01176240)., Methods: PD patients with documented nOH underwent ≤ 2 weeks of double-blind droxidopa or placebo dosage optimization followed by 8 weeks of maintenance treatment (100-600 mg t.i.d.). The primary efficacy measure was change in Orthostatic Hypotension Questionnaire (OHQ) composite score from baseline to Week 8. Key secondary variables included dizziness/lightheadedness score (OHQ item 1) and patient-reported falls., Results: Among 24 droxidopa and 27 placebo recipients, mean OHQ composite-score change at Week 8 was -2.2 versus -2.1 (p = 0.98); in response to this pre-planned futility analysis, the study was temporarily stopped and all data from these patients were considered exploratory. At Week 1, mean dizziness/lightheadedness score change favored droxidopa by 1.5 units (p = 0.24), with subsequent numerical differences favoring droxidopa throughout the observation period, and at Week 1, mean standing systolic blood-pressure change favored droxidopa by 12.5 mmHg (p = 0.04). Compared with placebo, the droxidopa group exhibited an approximately 50% lower rate of reported falls (p = 0.16) and fall-related injuries (post-hoc analysis)., Conclusions: This exploratory analysis of a small dataset failed to show benefit of droxidopa, as compared with placebo by the primary endpoint. Nonetheless, there were signals of potential benefit for nOH, including improvement in dizziness/lightheadedness and reduction in falls, meriting evaluation in further trials.
- Published
- 2014
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24. Two single-center, double-blind, randomized, placebo-controlled, phase I studies to investigate the tolerability and pharmacokinetics of CH-1504, an antifolate, in healthy male subjects.
- Author
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Mant T, Jurcevic S, Szakacs C, Adams L, Boland J, and Hewitt LA
- Subjects
- Adult, Aminopterin administration & dosage, Aminopterin adverse effects, Aminopterin pharmacokinetics, Dose-Response Relationship, Drug, Double-Blind Method, Drug Eruptions etiology, Folic Acid Antagonists adverse effects, Humans, Male, Molecular Structure, Aminopterin analogs & derivatives, Folic Acid Antagonists administration & dosage, Folic Acid Antagonists pharmacokinetics
- Abstract
Background: Several studies have suggested that a significant proportion of the toxicity profile of the antifolate methotrexate can be attributed to its hydroxylated and polyglutamylated metabolites. CH-1504 is an investigational antifolate, which is neither hydroxylated or polyglutamylated., Objective: The purpose of this study was to test the tolerability and pharmacokinetics of single and multiple ascending doses of CH-1504., Methods: Two single-center, double-blind, randomized, placebo-controlled, Phase I studies were conducted in single and multiple ascending-dose designs in healthy male adult volunteers. In the single ascending-dose study, subjects were randomized to receive the study drug (1, 5, 7.5, 10, 15, or 20 mg) or placebo in a 4:1 ratio. Subjects were under clinical supervision for 48 hours following a single oral administration. Follow-up occurred on days 10 and 30. In the multiple ascending-dose study, subjects were randomized to receive the study drug (7.5, 10, or 15 mg) or placebo at a 3:1 ratio. Subjects received a single oral administration of CH-1504 once daily on days 1 through 7, during which time they remained under clinical supervision. Follow-up was conducted on days 16 and 30. Tolerability was determined through echocardiogram and clinical laboratory tests (eg, hematology, serum biochemistry, urinalysis)., Results: No clinically significant abnormalities were observed in any of the tolerability evaluations. No adverse events were attributed to treatment and those that were possibly related (eg, rash, headache, dizziness) were all considered mild. Peak plasma concentrations occurred between 1 to 2.5 hours after administration and the apparent t(1/2) was approximately 3 hours. On average, <3.1% of the administered dose was recovered as CH-1504 in the urine in the single-dose study and <1.5% in the multiple-dose study., Conclusions: CH-1504 appeared to be well tolerated in single administered doses up to 20 mg and daily administrations for 7 days up to 15 mg in healthy male volunteers in these studies. However, the results of the pharmacokinetic analysis support the development of a new formulation to improve the bioavailability before further clinical studies are warranted.
- Published
- 2008
- Full Text
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25. Friendship group identification, multidimensional self-concept, and experience of developmental tasks in adolescence.
- Author
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Tarrant M, MacKenzie L, and Hewitt LA
- Subjects
- Adolescent, Female, Humans, Interpersonal Relations, Male, Sex Factors, Social Change, Surveys and Questionnaires, Adolescent Development, Friends, Self Concept, Social Identification
- Abstract
This study applied a social identity perspective to the study of adolescent self-concept and social development. British adolescents aged 14-15 years (N=114) completed a questionnaire which asked them to: (i) rate their degree of identification with a school-based friendship group; (ii) complete a measure of multi-dimensional self-concept; and (iii) report their experiences of a variety of personal, relational and socio-institutional (e.g., achieving economic independence) developmental tasks. Compared to low identifiers, participants who were highly identified with a friendship group reported highest levels of self-esteem; and these differences were most marked in non-academic domains of self. High identifiers also displayed higher levels of general self-esteem and reported more positive experiences of personal and relational developmental tasks. The discussion focuses on the potential benefits to understanding of social developmental processes that can be derived from a consideration of adolescents' subjective appraisals of their peer relations.
- Published
- 2006
- Full Text
- View/download PDF
26. Characterization of a major neutralizing epitope on human papillomavirus type 16 L1.
- Author
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White WI, Wilson SD, Palmer-Hill FJ, Woods RM, Ghim SJ, Hewitt LA, Goldman DM, Burke SJ, Jenson AB, Koenig S, and Suzich JA
- Subjects
- Animals, Antibodies, Monoclonal immunology, Binding, Competitive, Immunization, Mice, Mice, Inbred BALB C, Structure-Activity Relationship, Virion immunology, Antibodies, Viral immunology, Epitopes, Oncogene Proteins, Viral immunology, Papillomaviridae immunology
- Abstract
Persistent infection with human papillomavirus type 16 (HPV-16) is strongly associated with the development of cervical cancer. Neutralizing epitopes present on the major coat protein, L1, have not been well characterized, although three neutralizing monoclonal antibodies (MAbs) had been identified by using HPV-16 pseudovirions (R. B. Roden et al., J. Virol. 71:6247-6252, 1997). Here, two of these MAbs (H16.V5 and H16.E70) were demonstrated to neutralize authentic HPV-16 in vitro, while the third (H16.U4) did not. Binding studies were conducted with the three MAbs and virus-like particles (VLPs) composed of the reference L1 sequence (114K) and three variant L1 sequences: Rochester-1k (derived from viral stock DNA), GU-1 (derived from cervical biopsy DNA), and GU-2 (derived from biopsy DNA, but containing some sequence changes likely to be artifactual). While all three MAbs bound to 114K and Rochester-1k VLPs, GU-1 VLPs were not recognized by H16.E70, and both H16.E70 and H16.V5 failed to bind to GU-2 VLPs. Site-directed mutagenesis was used to replace disparate amino acids in the GU-2 L1 with those found in the 114K L1. Alteration of the amino acid at position 50, from L to F, completely restored H16.V5 binding and partially restored H16.E70 binding, while complete restoration of H16.E70 binding occurred with GU-2 VLPs containing both L50F and T266A alterations. Immunization of mice with L1 variant VLPs revealed that GU-2 VLPs were poorly immunogenic. The L50F mutant of GU-2 L1, in which the H16.V5 epitope was restored, elicited HPV-16 antibody responses comparable to those obtained with 114K VLPs. These results demonstrate the importance of the H16.V5 epitope in the generation of potent HPV-16 neutralizing antibody responses.
- Published
- 1999
- Full Text
- View/download PDF
27. Two different schedules for integrating filgrastim as adjuvant therapy in the treatment of patients with advanced stage Hodgkin's lymphoma receiving MOPP/ABV hybrid chemotherapy.
- Author
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Cantin G, L'Espérance B, Yelle L, Desjardins L, Couture F, Bergeron M, Lacroix L, Dufresne J, Bélanger D, Ouellet PA, Hewitt LA, Pirc L, and Gyger M
- Subjects
- Adolescent, Adult, Female, Filgrastim, Humans, Male, Mechlorethamine administration & dosage, Middle Aged, Neoplasm Staging, Prednisone administration & dosage, Procarbazine administration & dosage, Recombinant Proteins, Vincristine administration & dosage, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Granulocyte Colony-Stimulating Factor administration & dosage, Hodgkin Disease drug therapy
- Abstract
Purpose: Management of advanced-stage Hodgkin's disease with a MOPP/ABV hybrid regimen (mechlorethamine, vincristine, procarbazine, prednisone, Adriamycin, bleomycin and vinblastine) has yielded a high complete response rate (75-85%). However, myelosuppression can limit delivery of treatment. Filgrastim has been shown to reduce chemotherapy-related neutropenia and allow for on-time administration of planned doses of chemotherapeutic agents. The objective of this study was to find the best way to integrate filgrastim with the MOPP/ABV hybrid regimen., Methods: Enrolled in this study were 24 patients (aged 18-52 years) with newly diagnosed, histologically documented Hodgkin's disease. In schedule I, patients received filgrastim (5 microg/kg s.c. daily) beginning on day 9, 24 h after administration of ABV. In schedule II, patients received filgrastim concomitantly with procarbazine on days 2-7 (starting 24 h after day-1 MOPP administration and stopping 24 h before ABV administration) as well as after ABV beginning on day 9. Filgrastim after ABV administration was administered until two consecutive ANC readings of 10 x 10(9)/l were achieved., Results: All patients were able to complete all six cycles of therapy. There was a trend to fewer dose reductions in schedule II (0.76%) as compared to schedule I (4.2%) with a P-value of 0.077 (chi-squared test). Specifically, 11.6% of MOPP courses and 5.5% of ABV courses were dose-reduced in schedule I versus 1.7% and 1.4%, respectively, in schedule II., Conclusion: In conclusion, filgrastim was effective in supporting the delivery of the MOPP/ABV chemotherapy. Concomitant administration of filgrastim with procarbazine (days 2-7) appears to be safe and allows the maximum dose intensity of this therapy.
- Published
- 1999
- Full Text
- View/download PDF
28. Evidence for the involvement of organelles in the mechanism of ketone-potentiated chloroform-induced hepatotoxicity.
- Author
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Hewitt LA, Palmason C, Masson S, and Plaa GL
- Subjects
- Animals, Cytochrome P-450 Enzyme System metabolism, Drug Synergism, Liver ultrastructure, Lysosomes drug effects, Lysosomes metabolism, Male, Mitochondria, Liver drug effects, Mitochondria, Liver metabolism, Organelles metabolism, Oxygen Consumption drug effects, Rats, Rats, Inbred Strains, Chloroform toxicity, Ketones toxicity, Liver drug effects, Organelles drug effects
- Abstract
Ketones can potentiate the hepatotoxicity of haloalkanes in animals. This may be due, in part, to changes in organelle susceptibility. Male Sprague-Dawley rats were administered 15 mmol/kg (po) acetone, 2-butanone, 2-hexanone or 50 mg/kg (po) chlordecone or mirex (a nonketonic analog of chlordecone). Eighteen hours later, tests of organelle structure/function were performed (osmotic stress, respiration, and calcium pump activity). Other rats were given 14CHCl3 (0.5 or 1.0 ml/kg, po) 18 h after chlordecone or mirex administration. Three hours later, the organelle distribution of 14C was evaluated. In a final experiment, ketone-pretreated (chlordecone or 2-hexanone) animals were killed 6 h after CHCl3 administration and evaluated morphologically for evidence of modified organelle response. Acetone and chlordecone, when given alone, enhanced lysosomal fragility to osmotic stress; no changes in functional capacity of mitochondria or microsomes were observed. CHCl3-derived 14C in the mitochondrial fraction increased 2-fold in chlordecone-treated rats. Morphological evaluation suggested mitochondria respond differently to CHCl3 in ketone-pretreated (chlordecone or 2-hexanone) animals compared to corn oil-pretreated controls. These results support the concept that modifications of organelles contribute to the mechanism of ketone-potentiation of CHCl3-induced hepatotoxicity.
- Published
- 1990
- Full Text
- View/download PDF
29. Antithrombin III profiles in malignancy, relationship primary tumors and metastatic sites.
- Author
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Honegger H, Anderson N, Hewitt LA, and Tullis JL
- Subjects
- Breast Neoplasms blood, Colonic Neoplasms blood, Female, Fibrin Fibrinogen Degradation Products analysis, Humans, Liver Neoplasms blood, Liver Neoplasms secondary, Lung Neoplasms blood, Lymphoma blood, Male, Neoplasm Metastasis, Ovarian Neoplasms blood, Serum Albumin analysis, Antithrombin III analysis, Neoplasms blood
- Abstract
Variations of antithrombin III were studied in a non-randomized population of consecutive cancer cases admitted to a referral hospital. Differences between functional and immunologic assay were observed. Decreases were observed in both assays when compared to a population of hospitalized controls. Patients with cancer of the colon, ovary and prostate showed a deficiency of antithrombin III more frequently than other common tumors. When all tumor cases were subdivided into those in remission compared to those with metastases, a significant decrease in antithrombin III also could be shown. Metastases to the liver were strikingly common in cancer patients with decreased antithrombin III. In these patients, the decrease in antithrombin III could be statistically correlated with reduction in serum albumin.
- Published
- 1981
30. Fractional hepatic localization of 14CHCl3 in mice and rats treated with chlordecone or mirex.
- Author
-
Hewitt LA, Hewitt WR, and Plaa GL
- Subjects
- Animals, Carbon Radioisotopes, Cytochrome P-450 Enzyme System biosynthesis, Enzyme Induction drug effects, Male, Mice, Rats, Rats, Inbred Strains, Chlordecone toxicity, Chloroform metabolism, Insecticides toxicity, Liver metabolism, Mirex toxicity
- Abstract
In rodents chlordecone, but not mirex, a nonketonic structural analog, significantly augments CHCl3-induced liver damage, at least in part, by increasing CHCl3 bioactivation. To determine whether the fractional distribution of CHCl3 was altered in chlordecone-pretreated animals, the irreversible binding of 14CHCl3 to various liver constituents (a measure of CHCl3 bioactivation) was examined in vivo in mice and rats. Chlordecone, but not mirex, increased both total and irreversibly bound 14CHCl3; furthermore, changes in the 14C localization between lipid, protein and acid-soluble fractions were noted. Thus, the results suggest that differences exist between chlordecone and mirex with respect to their capacity to increase the quantity of CHCl3-derived reactive metabolite and the eventual distribution of reactive metabolite.
- Published
- 1983
- Full Text
- View/download PDF
31. Modifications in rat hepatobiliary function following treatment with acetone, 2-butanone, 2-hexanone, mirex, or chlordecone and subsequently exposed to chloroform.
- Author
-
Hewitt LA, Ayotte P, and Plaa GL
- Subjects
- Acetone toxicity, Animals, Bile drug effects, Bile metabolism, Butanones toxicity, Chlordecone toxicity, Drug Interactions, Male, Methyl n-Butyl Ketone toxicity, Mirex toxicity, Permeability, Rats, Rats, Inbred Strains, Biliary Tract drug effects, Chloroform toxicity, Ketones toxicity, Liver drug effects
- Abstract
Potentiation of haloalkane hepatonecrosis by various ketones is a well-documented observation. The present study investigates the hepatobiliary effects of such treatments. Male Sprague-Dawley rats were pretreated with acetone (A), 2-butanone (MEK), 2-hexanone (MBK), 15 mmol/kg (po), or chlordecone (CD) and its nonketonic analog, mirex (M), 50 mg/kg (po). Following the pretreatment at various time intervals ranging from 10 to 96 hr, groups of animals received a challenging dosage of CHCl3 (0.5 ml/kg, po). In a collateral experiment, groups of animals were pretreated with vehicle and 18 hr later received either 0.50, 0.75, or 1.00 ml/kg CHCl3 (po). In each case hepatobiliary function was evaluated 24 hr later using bile flow rate and plasma bilirubin concentration. The results showed (1) that the ketones alone had no effect; mirex alone increased bile flow; (2) CHCl3 alone had no effect on bile flow but slightly increased plasma bilirubin; (3) all pretreatments potentiated the effect of CHCl3 on plasma bilirubin; (4) combinations of A, MBK, or CD plus CHCl3 were cholestatic within a restricted time frame. A study of biliary tree permeability by the segmented retrograde intrabiliary injection technique, using mannitol and inulin as marker compounds, suggested that cholestasis may result from potentiation of CHCl3-induced alterations in canalicular membrane permeability.
- Published
- 1986
- Full Text
- View/download PDF
32. Dose-response relationships in 1,3-butanediol-induced potentiation of carbon tetrachloride toxicity.
- Author
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Hewitt WR, Miyajima H, Côté MG, Hewitt LA, Cianflone DJ, and Plaa GL
- Subjects
- Animals, Biotransformation drug effects, Body Weight drug effects, Drug Synergism, Glutathione metabolism, Ketones urine, Liver enzymology, Male, Mixed Function Oxygenases metabolism, Rats, Rats, Inbred Strains, Butylene Glycols toxicity, Carbon Tetrachloride toxicity
- Published
- 1982
- Full Text
- View/download PDF
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