Search

Objective: This study investigated the effect of varenicline on the multiple-dose pharmacokinetics of digoxin., Methods: Eighteen smokers were randomized to receive digoxin (Lanoxicaps 0.2 mg QD) with varenicline 1 mg BID or placebo for 14 days., Results: Varenicline had no clinically relevant effect on the digoxin steady-state exposure, as evidenced by the 90% confidence intervals for the ratios of AUC(0-24) (87.5-108%) and C(min) (83.8-116%) wholly contained within 80-125%. Digoxin C(max) and T(max) remained unchanged in the presence of varenicline, consistent with no apparent alteration in digoxin bioavailability. A minimal 11.3% increase in digoxin renal clearance was noted during varenicline treatment while having no impact on its systemic exposure. Results are supported by mechanistic evidence in Caco-2 cell monolayers that varenicline is neither a P-gp substrate nor an inhibitor of P-gp-mediated efflux of digoxin. Co-administration of varenicline and digoxin was well tolerated., Conclusion: The results suggest that digoxin can be safely administered with varenicline without the need for dose adjustment.

Tmax is the time associated with the maximum serum or plasma drug concentration achieved following a dose. While Tmax is continuous in theory, it is usually discrete in practice because it is equated to a nominal sampling time in the noncompartmental pharmacokinetics approach. For a 2-treatment crossover design, a Hodges-Lehmann method exists for a confidence interval on treatment differences. For appropriately designed crossover studies with more than two treatments, a new median-scaling method is proposed to obtain estimates and confidence intervals for treatment effects. A simulation study was done comparing this new method with two previously described rank-based nonparametric methods, a stratified ranks method and a signed ranks method due to Ohrvik. The Normal theory, a nonparametric confidence interval approach without adjustment for periods, and a nonparametric bootstrap method were also compared. Results show that less dense sampling and period effects cause increases in confidence interval length. The Normal theory method can be liberal (i.e. less than nominal coverage) if there is a true treatment effect. The nonparametric methods tend to be conservative with regard to coverage probability and among them the median-scaling method is least conservative and has shortest confidence intervals. The stratified ranks method was the most conservative and had very long confidence intervals. The bootstrap method was generally less conservative than the median-scaling method, but it tended to have longer confidence intervals. Overall, the median-scaling method had the best combination of coverage and confidence interval length. All methods performed adequately with respect to bias., ((c) 2007 John Wiley & Sons, Ltd.)

This study investigated the effect of varenicline on the pharmacokinetics and pharmacodynamics of a single dose of warfarin in 24 adult smokers and compared these findings with data generated using human in vitro systems. Subjects were randomized to receive varenicline 1 mg twice a day or placebo for 13 days and then switched to the alternative treatment after a 1-week washout period. A single dose of warfarin 25 mg was given on day 8 of each treatment period, and serial blood samples were collected over 144 hours postdose. Pharmacokinetic parameters for both (R)- and (S)-warfarin and international normalized ratio (INR) values were determined. Varenicline was assessed as an inhibitor and inducer of human cytochrome P450 activities using liver microsomes and hepatocytes, respectively. Consistent with the in vitro data, no alteration in human pharmacokinetics of warfarin enantiomers was observed with varenicline treatment. The 90% confidence intervals for the ratios of area under the concentration-time curve from zero hours to infinity and peak plasma concentrations were completely contained within 80% to 125%. Warfarin pharmacodynamic parameters, maximum INR, and the area under the prothrombin (INR)-time curve, were also unaffected by steady-state varenicline. Concomitant administration of varenicline and warfarin was well tolerated. Consequently, warfarin can be safely administered with varenicline without the need for dose adjustment.

Average bioequivalence (ABE) has been the regulatory standard for bioequivalence (BE) since the 1990s. BE studies are commonly two-period crossovers, but may also use replicated designs. The replicated crossover will provide greater power for the ABE assessment. FDA has recommended that ABE analysis of replicated crossovers use a model which includes terms for separate within- and between-subject components for each formulation and which allows for a subject x formulation interaction component. Our simulation study compares the performance of four alternative mixed effects models: the FDA model, a three variance component model proposed by Ekbohm and Melander (EM), a random intercepts and slopes model (RIS) proposed by Patterson and Jones, and a simple model that contains only two variance components. The simple model fails (when not 'true') to provide adequate coverage and it accepts the hypothesis of equivalence too often. FDA and EM models are frequently indistinguishable and often provide the best performance with respect to coverage and probability of concluding BE. The RIS model concludes equivalence too often when both the within- and between-subject variance components differ between formulations. The FDA analysis model is recommended because it provides the most detail regarding components of variability and has a slight advantage over the EM model in confidence interval length.

Objective: This study compares the time-action profile of inhaled insulin (INH; Exubera) with that of subcutaneously injected insulin lispro (ILP) or regular human insulin (RHI) in healthy volunteers., Research Design and Methods: In this open-label, randomized, three-way, crossover study, 17 healthy male volunteers were given each of the following treatments in random order: INH (6 mg), ILP (18 units), or RHI (18 units). Glucose infusion rates and serum insulin concentrations were monitored over 10 h., Results: INH had a faster onset of action than both RHI and ILP, as indicated by shorter time to early half-maximal effect (32 vs. 48 and 41 min, respectively; P < 0.001 for IHN vs. RHI and P < 0.05 for IHN vs. ILP). Time to maximal effect was comparable between INH and ILP (143 vs. 137 min; NS) but was shorter for INH than RHI (193 min; P < 0.01). The maximal metabolic effect of INH was comparable with RHI but lower than ILP (8.7 vs. 9.8 vs. 11.2 mg . kg(-1) . min(-1), respectively; P < 0.01 for INH vs. ILP). The duration of action of INH, indicated by time to late half-maximal effect (387 min), was longer than ILP (313 min; P < 0.01) and comparable to RHI (415 min; NS). Total glucodynamic effect after inhalation of INH was comparable to both ILP and RHI (NS). Relative bioefficacy of INH was 10% versus RHI and 11% versus ILP. No drug-related adverse events were observed., Conclusions: INH had a faster onset of action than RHI or ILP and a duration of action longer than ILP and comparable to RHI. These characteristics suggest that inhaled insulin is suitable for prandial insulin supplementation in patients with diabetes.

Treatment with some quinolones is associated with an abnormal skin reaction following exposure to sunlight (photosensitivity). The objective of the current study was to compare the photosensitizing potential of a new quinolone, trovafloxacin, with that of ciprofloxacin, lomefloxacin and placebo. Forty-eight healthy males (age range 19-45 years) were randomized to receive a 7 day course of treatment with: (i) trovafloxacin 200 mg od; (ii) ciprofloxacin 500 mg bd; (iii) lomefloxacin 400 mg od; or (iv) placebo bd. Minimal erythema doses (MEDs) were assessed using a monochromator at baseline and on day 5 of treatment, for wavelengths of 305 +/- 5, 335 +/- 30, 365 +/- 30, 400 +/- 30 and 430 +/- 30 nm; 335 +/- 30 and 365 +/- 30 nm are within the UVA range. Immediate reaction MEDs were similar in all treatment groups. However, between baseline and day 5, the mean decreases in delayed-reaction MED (24 h) at 335 +/- 30 nm were only 18.99% for trovafloxacin versus placebo (P = 0.1267), compared with 53.77% (P 0.0001) and 64.13% (P 0.0001) for ciprofloxacin and lomefloxacin, respectively. Similarly, at 365 +/- 30 nm, trovafloxacin produced the smallest reduction in delayed MED versus placebo (43.66%), compared with ciprofloxacin (61.53%) and lomefloxacin (75.81%). These differences between trovafloxacin and ciprofloxacin and lomefloxacin were significant at both 335 +/- 30 and 365 +/- 30 nm (P 0.029). All MED values returned to baseline levels within 2 days of drug cessation. These results show that trovafloxacin has significantly less photosensitizing potential than either ciprofloxacin or lomefloxacin. This photosensitivity appears to be induced only by wavelengths in the UVA region, is maximal at 24 h and is a short-term effect.

Background: Morphine and antibiotics are frequently coadministered in the surgical setting. These agents may interact, reducing the efficacy of the antibiotic or increasing the toxicity of morphine. It is therefore important to determine whether antibiotics that might be used for surgical prophylaxis have the potential to change the pharmacokinetics of morphine. It is equally important to learn whether morphine affects the plasma levels of antibiotics and thus may potentially influence their efficacy or tolerability., Methods: This open, randomized, placebo-controlled, three-treatment, three-period cross-over study enrolled 19 healthy volunteers. Oral trovafloxacin (200 mg), a novel fluoroquinolone antibiotic, and intravenous morphine (0.15 mg/kg) were coadministered, and the effects on the pharmacokinetics of each drug and on changes in the pharmacologic action of morphine, estimated from its effects on respiratory rate and level of sedation, were examined., Results: When trovafloxacin was coadministered with morphine, the half-life of trovafloxacin was unchanged; however, the ratio of the area under the serum concentration versus time curve (AUC(0-infinity)) estimates for trovafloxacin/morphine versus trovafloxacin/placebo was 63.8% (95% confidence interval [CI], 40.7% to 100.3%), indicating a 36% reduction in the bioavailability of trovafloxacin. The ratio of the mean maximum serum concentration (Cmax) estimates of trovafloxacin for the two treatments was 53.8% (95% CI: 36.1% to 80.1%), indicating a 46% reduction in Cmax. The time to Cmax was delayed by 4 hours. With trovafloxacin coadministration, there were no statistically significant changes in either the mean relative bioavailability of morphine or that of its metabolite, 6beta-glucuronide-morphine. Coadministration of trovafloxacin did not exacerbate the reduction in respiratory rate or increase the number of side effects associated with morphine administration., Conclusions: Coadministration of trovafloxacin and morphine reduces the bioavailability and maximum serum concentrations of trovafloxacin. However, elimination of oral trovafloxacin is not impaired, suggesting that the efficacy of trovafloxacin could be maintained in many patients who receive concomitant morphine. Morphine plasma levels and pharmacologic effects are not significantly altered by coadministration of trovafloxacin. Despite their similar metabolic pathways, the trovafloxacin/morphine combination neither exacerbates the respiratory depressant effects of morphine nor increases the frequency of side effects when compared with placebo/morphine treatment. These results suggest that the efficacy of trovafloxacin may be maintained when coadministered with morphine. Concurrent administration of trovafloxacin and morphine is unlikely to alter the pharmacologic effects of morphine.

Background: Patients in the hospital, as well as those in home care settings, often require nutritional supplementation with enteral feeding solutions. In addition, patients with serious infections who are clinically unstable often cannot maintain adequate intake by mouth and may require an alternative to oral antibiotic administration. However, delivery of crushed oral formulations of drugs via nasogastric tubes is often carried out without adequate bioavailability data, and this method of administration may not always be equivalent to oral drug delivery., Methods: In an open-label, randomized, four-period, four-treatment, cross-over study, 24 healthy volunteers were given one dose of each of the following treatments, with a 7-day wash-out between dosing periods: Treatment A: two 100-mg trovafloxacin tablets given orally with 240 mL water; Treatment B: two crushed 100-mg trovafloxacin tablets suspended in water and administered through a nasogastric tube into the stomach; Treatment C: two crushed 100-mg trovafloxacin tablets suspended in water and administered through a nasogastric tube into the duodenum; or Treatment D: two crushed 100-mg trovafloxacin tablets suspended in water and given through a nasogastric tube into the stomach concomitantly with an enteral feeding solution (240 mL full-strength Osmolite)., Results: Pharmacokinetic analyses showed that the bioavailability of trovafloxacin after administration of crushed tablets into the stomach with or without concomitant enteral feeding was not significantly different from that of the orally administered whole tablets: the 90% confidence limits of the area under the concentration-time curve (AUC(0-infinity)) for Treatment B versus Treatment A (91.3%, 109.5%) and Treatment D versus Treatment A (91.6%, 109.9%) were well within the bioequivalence criteria of 80% to 125%. Results of analysis of variance (ANOVA) indicated no significant sequence, period, or treatment-by-period interaction effects. Administration of trovafloxacin into the duodenum (Treatment C) resulted in reduced systemic exposure to trovafloxacin, with a 31% decrease in AUC(0-infinity) and a 30% decrease in peak serum concentration (Cmax) compared to oral administration. Time to peak serum concentration (Tmax) was 1.7 hours after oral administration of trovafloxacin and 1.1 hours after administration directly into the stomach or duodenum through a nasogastric tube in the absence of concomitant enteral feeding. All four treatments were well tolerated; no participant discontinued the study due to adverse events and no serious adverse events were reported., Conclusions: These results showed that administration of crushed trovafloxacin tablets through a nasogastric tube into the stomach, with or without concomitant enteral feeding, achieves absorption and tolerability comparable to those of orally administered trovafloxacin tablets.

Background: Treatment with oral antibiotic drugs generally influences normal fecal flora. These changes can be both beneficial (eg, elimination of aerobic, gram-negative bacilli) and detrimental (eg, the appearance of resistant pathogenic micro-organisms). Trovafloxacin, a new fluoroquinolone with in vitro activity against anaerobes, and gram-negative, gram-positive, and atypical pathogens, is a potentially beneficial antimicrobial for bowel sterilization. This double-blind trial investigated the effect of trovafloxacin on the normal microbial bowel flora of healthy male subjects., Methods: Subjects were randomized (in a 2:1 ratio) to receive either 200 mg trovafloxacin once daily for 10 days or a matching placebo. Fecal samples were collected at two baseline occasions, on visit days 4, 7, 10, and 17, and at follow-up. Bacterial species were identified and quantified in the fecal samples., Results: Twelve subjects received the active drug and seven received placebo. No Enterobacteriaceae were found in samples from days 4 to 10 in subjects receiving trovafloxacin. No changes in Enterobacteriaceae were found throughout the study in subjects receiving placebo. Incidental Enterobacteriaceae were isolated from subjects in the trovafloxacin group at the end of the study. No clinically significant differences were found in either group with respect to prevalence, appearance, or disappearance of aerobic gram-positive cocci, anaerobic bacteria, or yeasts. All tested Enterobacteriaceae were highly susceptible to trovafloxacin. No increase in minimum inhibitory concentration values was seen in day 17 and follow-up samples for isolated Escherichia coli strains. No Clostridium difficile was found in day 17 or follow-up samples from subjects in the trovafloxacin group. All tests for clostridium toxin were negative., Conclusions: During the treatment period, E. coli could not be cultured from the feces of the 12 healthy subjects receiving 200 mg trovafloxacin daily during days 4 to 10. All isolated Enterobacteriaceae were susceptible to trovafloxacin and no changes in susceptibility were found after the treatment period. In subjects treated with trovafloxacin, the prevalence and number of gram-positive bacteria were rapidly reduced. Trovafloxacin is able to selectively and reversibly suppress bowel flora.

A simplified dosing algorithm for trovafloxacin was evaluated following a single-dose infusion of alatrofloxacin at trovafloxacin equivalent doses of 30, 100, 200, 300 and 400 mg (57 subjects), and multiple doses of 200, 300 and 400 mg (30 subjects). Maximum serum concentration and area under the concentration-time curve for trovafloxacin increased with dose. Trovafloxacin clearance (82-85 ml x h/kg) and volume of distribution (1.3-1.6 l/kg) were independent of dose. Infusion of alatrofloxacin at a trovafloxacin equivalent dose of 300 mg at 1, 2 or 3 mg/ml over 1 h did not alter the pharmacokinetics of trovafloxacin. A plot of the weight-adjusted dose of trovafloxacin in individual subjects against the maximum serum concentration following single and multiple dosing, indicated that the maximum serum concentration increased 1 microg/ml for each 1 mg/kg of trovafloxacin administered. Thus, a prior knowledge of the desired serum concentration will permit appropriate dosing without the use of complex nomograms in patients with normal hepatic function.

Twelve healthy male volunteers participated in this open, randomized, placebo-controlled, two-way crossover study to investigate the effects of cimetidine on the steady-state pharmacokinetics of oral trovafloxacin. Volunteers were randomized to receive either 400 mg cimetidine twice daily or placebo for 5 days. From day 3-5, volunteers received 200 mg trovafloxacin once daily in addition to either cimetidine or placebo. After a minimum 7-day washout period, the study was repeated: those volunteers who received placebo during the first study period were administered cimetidine, and vice versa. The maximum observed serum trovafloxacin concentration, the area under the concentration-time curve of trovafloxacin within the dosing interval of 24 h and the earliest time to the maximum serum concentration for trovafloxacin in volunteers receiving concomitant cimetidine were 2.4 microg/ml. 27.8 microg x h/ml and 1.4 h, respectively, compared with 2.5 microg/ml, 27.1 microg x h/ml and 1.5 h, respectively, in volunteers receiving concomitant placebo. Thus. multiple dosing with cimetidine had no significant effect on the absorption or disposition of trovafloxacin at steady state. Co-administration of cimetidine and trovafloxacin was also well tolerated and without serious adverse effects.

Present product labelling indicates that azithromycin capsules should not be taken with food. However, three recent studies demonstrated that food does not significantly decrease the bioavilabilities of three new formulations of azithromycin (250 mg tablets, 1000 mg sachet, 500 mg paediatric suspension). With a 500 mg dosage, the mean relative bioavailability of azithromycin following ingestion of a standard high-fat breakfast was 96% when administered as two 250 mg tablets and 113% when administered as a suspension. The mean relative bioavailability of a 1000 mg sachet was 112%. The absolute bioavailability of the sachet formulation, relative to a 1 h iv infusion of 1000 mg, was 44%. Thus, azithromycin tablets, suspension and sachet may be given without regard to meals, further enhancing the convenience of once-daily, short-duration dosing regimens.

A validation procedure is presented that satisfies the FDA requirements of accuracy (including precision repeatability), sensitivity, linearity, dynamic range, and homoscedasticity, all with a single set of data. The procedure utilizes the corrigible error correction (CEC) technique comprised of three response curves--standard, Youden one-sample, and method of standard additions (MOSA) plots, from a total of 15 to 18 X,Y data pairs. For the bias component of accuracy, the systematic bias error of the method is quantitatively separated into its constant and proportional error components. The overall constant systematic error is further separated into the system (blank) and analyte-matrix (sample) components. The CEC data also provide an internal, i.e., in situ corrected assay for the sample for comparison with alternative method data. Statistical diagnostic tests are used for the final evaluation of the method acceptability, specifically in deciding whether or not the systematic error indicated requires a root source search for its removal or is simply a calibration constant of the method.