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Introduction: Hypokalaemia is a potentially life-threatening adverse event of flucloxacillin with unknown incidence. The risk of flucloxacillin-induced hypokalaemia has recently been suggested to be increased among females compared to males. The aim of this study is to describe the incidence and to determine the influence of sex and other risk factors on flucloxacillin-induced hypokalaemia., Methods: A retrospective single-centre cohort study was performed. Patients treated with intravenous flucloxacillin for >24 hours between January 2017 and October 2020, a baseline potassium level of ≥3.5 mmol/L and potassium measurement during treatment were included. The primary endpoint was incidence of hypokalaemia defined as the percentage of patients with a potassium measurement <3.5 mmol/L during flucloxacillin treatment. Logistic regression modelling was used to establish risk factors for hypokalaemia., Results: A total of 835 patients were included, 58.2% male and median age 71.0 years (interquartile range 61.0-81.0). The incidence of hypokalaemia was 23.7% (28.4% in females vs 20.4% in males). A dose-dependent relation between sex and the incidence of hypokalaemia was found. The risk of hypokalaemia was 4.41 (95% confidence interval 1.47-13.24) times higher in females compared to males when receiving a flucloxacillin dose of >8 g/24 h. No sex differences were found for lower daily doses. Other risk factors for hypokalaemia were older age, concomitant antibiotic use, lower bodyweight, lower baseline plasma potassium concentration and longer treatment duration., Conclusion: Hypokalaemia is a frequent complication in patients treated with intravenous flucloxacillin. Females receiving >8 g intravenous flucloxacillin per day are more prone to develop hypokalaemia compared to males., (© 2022 British Pharmacological Society.)

Aims: Selective serotonin re-uptake inhibitors (SSRIs), specifically citalopram and escitalopram, are thought to cause QTc prolongation, although studies have shown contradictory results. Nevertheless, a maximum citalopram dosage of 20 mg in high risk patients (e.g. >60 years of age) is recommended. We aimed to investigate the association between use of (individual) SSRIs and QTc in a population-based study in older adults., Methods: This study, which was part of the prospective Rotterdam Study (period 1991-2012), included participants with up to five electrocardiograms (ECGs). We used linear mixed models to compare QTc F (QT corrected according to Fridericia) measured during use of individual SSRIs with QTc F measured during non-use of any antidepressant. For citalopram, analyses were additionally restricted to a maximum dosage of 20 mg in participants aged 60 years and older., Results: We included 12 589 participants with a total of 26 620 ECGs of which 436 ECGs were made during SSRI use. The mean QTc F was similar during use of any drugs from the SSRI class and during non-use. After stratifying to individual SSRIs, ECGs recorded during use of citalopram had the longest QTc compared with ECGs recorded during non-use (+12.8 ms, 90% CI 7.5, 18.2). This result remained similar in the analysis comprising participants aged 60 years and older with a maximum prescribed daily dosage of 20 mg citalopram., Conclusions: Although no SSRI class effect was observed, use of citalopram was associated with a longer QTc F, even after considering the recommended restrictions. Other SSRIs may not give a clinically relevant QTc F prolongation., (© 2015 The British Pharmacological Society.)

Aims: Cardiovascular disease in women is often underestimated. The effects of cardiovascular drugs differ between the sexes because of pharmacokinetic and pharmacodynamic differences. Adverse drug reactions (ADRs) within these drug classes may have serious consequences, leading to hospital admission. We aimed to study differences between men and women in hospital admissions for ADRs due to cardiovascular drugs., Methods: We conducted a nationwide study of all hospital admissions between 2000 and 2005 with data from the Dutch National Medical Register. Relative risks were calculated of hospital admissions due to ADRs to the different cardiovascular drug groups for women compared with men. By an ecological design, risks were adjusted for the total number of Dutch inhabitants and the total number of prescriptions., Results: In total, 14 207 of the hospital admissions (34% of all ADR-related admissions) were attributed to cardiovascular drugs [7690 in women (54%; 95% confidence interval 53-55%)]. 'Anticoagulants and salicylates' (n= 8988), 'high- and low-ceiling diuretics' (n= 2242) and 'cardiotonic glycosides' (n= 932) were responsible for the majority of the ADR-related hospital admissions. The most pronounced sex differences were seen in users of low-ceiling diuretics (relative risk 4.02; 95% confidence interval 3.12-5.19), cardiotonic glycosides (relative risk 2.38; 95% confidence interval 2.06-2.74), high-ceiling diuretics (relative risk 2.10; 95% confidence interval 1.91-2.32) and coronary vasodilators (relative risk 0.77; 95% confidence interval 0.65-0.91)., Conclusions: Clear sex differences exist in ADRs requiring hospital admission for different cardiovascular drug groups. Sex differences should be taken into account in the prescription and evaluation of drugs., (© 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.)

Aim: The aim of this study was to investigate the effects of co-medication with selective serotonin re-uptake inhibitors (SSRIs) on overanticoagulation during acenocoumarol maintenance treatment., Methods: All subjects from The Rotterdam Study who received acenocoumarol maintenance treatment between April 1 1991 and September 9 2009 were followed for the event of an international normalized ratio (INR) ≥6, until death, end of treatment or end of the study period. With the Andersen-Gill extension of the Cox proportional hazards model, risks for repeated events of overanticoagulation in relation to concomitant SSRI use were calculated., Results: The risk for overanticoagulation during acenocoumarol maintenance treatment was increased in combination with fluvoxamine (HR 2.63, 95% CI 1.49, 4.66) and venlafaxine (HR 2.19, 95% CI 1.21, 3.99). There was no increase in risk for the other SSRIs, but numbers of exposed cases were low for all SSRIs except paroxetine., Conclusion: Fluvoxamine and venlafaxine were associated with a more than double risk of INR values ≥6 in acenocoumarol treated subjects., (© 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.)

What Is Already Known About This Subject: Women are more at risk for developing adverse drug reactions (ADRs) due to differences in pharmacokinetics, pharmacodynamics and drug use. ADRs regularly lead to hospital admissions., What This Study Adds: There are differences between the sexes in hospital admissions attributed to ADRs. The risk of being hospitalized with an ADR varies between the sexes in the type of reaction and the causative drug., Aim: Adverse drug reactions (ADRs) are a major burden in health care, regularly leading to hospital admission, morbidity or death. Women tend to have a higher risk of adverse drug reactions with a 1.5 to 1.7-fold greater risk than men. Our primary aim was to study differences in ADR-related hospitalizations between the sexes., Methods: We conducted a nationwide study of all ADR-related hospitalizations in the period between 2000 and 2005 in the Netherlands, which were selected from all 9,287,162 hospital admissions in this period. ADR-drug group combinations with at least 50 admissions in one of the sexes were selected. Relative risks and confidence intervals were calculated with respect to total admissions and total prescriptions with men as reference., Results: In total, 0.41% of the 4,236,368 admissions in men (95% CI 0.40, 0.42%) and 0.47% of the 5,050,794 admissions in women (95% CI 0.46, 0.48%) were attributed to an ADR by medical specialists (57% of all ADR-related admissions were in women). Differences between the sexes in risk for ADR-related hospitalization were found for antineoplastic and immunosuppressive drugs, antirheumatics, anticoagulants and salicylates, cardiovascular and neurological drugs, steroids and antibiotics. In certain drug categories, risks for hospitalization changed after taking into account total drug prescriptions., Conclusion: In all different drug classes, significant differences exist between the sexes in ADR-related hospital admissions. Cardiovascular drugs account for the most pronounced differences between men and women. More research is needed to explain the clear sex differences in ADR-related hospital admissions., (© 2010 The Authors. British Journal of Clinical Pharmacology © 2010 The British Pharmacological Society.)

Aim: To study the effect of the CYP2D6*4 polymorphism on serum sodium concentration in users of antidepressants [selective serotonin reuptake inhibitors and tricyclic antidepressants (TCAs)]., Methods: In this population-based cohort study, all subjects in the Rotterdam Study were included who used an antidepressant at baseline and from whom a blood sample was available in which CYP2D6 genotype and serum sodium concentration could be determined (n= 76). Multivariate linear regression was used to study the association between CYP2D6*4 and serum sodium concentration., Results: CYP2D6 poor metabolizers (PMs) (*4/*4) had a significantly lower mean serum sodium concentration in comparison with CYP2D6 extensive metabolizers (EMs) (*1/*1) [difference -3.9 mmol l(-1); 95% confidence interval (CI) -0.86, -7.03; P= 0.013]. In CYP2D6*4 heterozygotes (*1/*4) serum sodium concentration was 1.7 mmol l(-1) (95% CI -3.48, 0.18) lower compared with CYP2D6 EMs, but this difference was not statistically significant (P= 0.077)., Conclusions: The serum sodium concentration in PMs was lower in users of an antidepressant, especially in TCA users. Therefore CYP2D6 PMs might be at increased risk of developing symptoms of hyponatraemia.

Aim: Recently, a polymorphism in the NOS1AP gene (rs10494366), a regulator of neuronal nitric oxide synthase (nNOS), was associated with QTc prolongation. Both nNOS and calcium channel blockers (CCBs) regulate intracellular calcium levels and have an important role in cardiovascular homeostasis. The aim was to investigate whether this polymorphism is associated with cardiovascular mortality in users of CCBs., Methods: The data from the Rotterdam study, a population-based closed cohort study of Caucasian individuals of > or =55 years of age, were used. We identified 1113 participants in the Rotterdam Study who were prescribed CCBs for the first time between 1991 and 2005. All-cause and cardiovascular mortality was assessed in participants who were prescribed CCBs with different NOS1AP rs10494366 genotypes using Cox proportional hazard models., Results: In participants starting on dihydropyridine CCBs (amlodipine, nifedipine and others) all-cause mortality (n = 79) risks were higher in participants with the TG [hazard ratio (HR) 2.57, 95% confidence interval (CI) 1.24, 5.34] or the GG genotype (HR 3.18, 95% CI 1.18, 8.58) than in participants with the referent TT genotype. Cardiovascular mortality (n = 54) risks were 3.51 (95% CI 1.41, 8.78) for the TG genotype and 6.00 (95% CI 1.80, 20.0) for the GG genotype. No differences in all-cause mortality or cardiovascular mortality were seen in participants starting with the nondihydropyridine CCBs verapamil or diltiazem., Conclusion: The minor G allele of rs10494366 in the NOS1AP gene is associated with increased all-cause and cardiovascular mortality in Caucasian users of dihydropyridine CCBs. The mechanism underlying the observed association is unknown.

What Is Already Known About This Subject: * Most antidepressants are metabolized by CYP2D6. The variant allele CYP2D6*4 is the main polymorphism resulting in reduced enzyme activity in Caucasians. * Reduced enzyme activity potentially leads to increased toxicity of antidepressants, but the relevance of genotyping for clinical practice is unclear. Most clinical studies suffer from small numbers of patients., What This Study Adds: * This large population-based cohort study in 1198 elderly Dutch patients examines the influence of the CYP2D6*4 polymorphism on intolerability of antidepressants. * The risk of switching to another antidepressant in tricyclic antidepressant users is higher in poor metabolizers (PMs), but not in SSRI users. PMs require a lower maintenance dose of antidepressants compared with extensive metabolizers (EMs). * Antidepressants were initiated in a relatively low dose, with gradual dose increments thereafter, reducing the risk of adverse drug reactions. Therefore, the question remains whether genotyping prior to the start of antidepressant therapy contributes substantially to the optimization of pharmacotherapy., Aims: To study the effect of CYP2D6*4 on antidepressant dose, switching and discontinuation of therapy., Methods: The study consisted of all subjects in the Rotterdam Study, who received a first antidepressant prescription between April 1st 1991 and July 1st 2005 and for whom data on CYP2D6 genotype were available. Binary logistic regression was performed to study the association between CYP2D6*4 and switching to any other antidepressant or discontinuation of therapy within 45 days. The difference in mean antidepressant dose was compared between CYP2D6 genotypes using t-tests and repeated measurements analyses., Results: In users of tricyclic antidepressants (TCAs) the risk of switching to another antidepressant was significantly higher in poor metabolizers (PMs:*4/*4) compared with extensive metabolizers (EMs:*1/*1), with an adjusted OR of 5.77 (95% CI 1.59, 21.03; P = 0.01). In SSRI users there was no significant difference (OR 0.91; 95% CI 0.20, 4.15; P = 0.90). Heterozygous patients did not have an increased risk of switching in both TCA and SSRI users. The mean TCA dose was significantly lower in PMs than in EMs at the third and fourth prescription (difference 0.11 DDD, P = 0.03). In SSRI users the difference in mean dose between PMs and EMs was significant at the third prescription (0.17 DDD; P = 0.02)., Conclusions: The risk of switching to another antidepressant in TCA users is higher in PMs than in EMs. The maintenance doses of antidepressants were significantly lower in PMs. However, the question whether genotyping prior to the start of antidepressant therapy contributes substantially to the optimization of pharmacotherapy, requires further study.

Some medical textbooks on drug interactions take note of the potential interaction between laxatives and coumarin anticoagulants, but epidemiological evidence that this interaction is of practical importance is lacking. We conducted a follow-up study in a large population-based cohort to investigate which laxatives are associated with overanticoagulation during therapy with coumarins. Of the 1124 patients in the cohort, 351 developed an International Normalized Ratio > or = 6.0. The only laxative with a moderate but significantly increased relative risk of overanticoagulation was lactulose (relative risk 3.4, 95% confidence interval 2.2, 5.3). In view of the widespread use of lactulose, especially among the elderly, awareness of this potential drug interaction is required.

Aims: To establish the frequency with which NSAIDs were prescribed to elderly patients after admission to hospital for serious gastrointestinal complications and to study which factors are determinants of the prescription of these contraindicated drugs., Methods: A retrospective cohort study of patients from The Rotterdam Elderly Study, a prospective population-based cohort study of people older than 55 years of age was carried out. Elderly patients with a hospital admission for serious gastrointestinal complications were followed until prescription of an NSAID, death, removal to another area or end of the study period, whichever came first. The following baseline determinants for receiving a contraindicated prescription were studied: gender, age, presence of rheumatoid arthritis or osteoarthritis, presence of cardiovascular risk factors, number of GP visits, number of visits to a medical specialist, cognitive function and the prescriber being a GP or a medical specialist., Results: Prescriptions of an NSAID after discharge from hospital, were identified in 73 patients (73%). Fifty-one percent were prescribed aspirin of whom the large majority used it as an antithrombotic agent, and 49% were prescribed a nonaspirin NSAID after discharge from hospital. Twenty percent of the patients used more than one NSAID on one or more occasions after discharge. For patients who were prescribed NSAIDs before admission as well as after discharge, the proportion of contraindicated prescriptions with concomitant use of antiulcer drugs rose significantly from 0.19 before discharge to 0.60 after discharge for aspirin and from 0.11 to 0.61 for nonaspirin NSAIDs. In the multivariate analysis the only remaining factor with prognostic influence on prescription of NSAIDs was a history of NSAID use before cohort enrollment. A history of rheumatoid arthritis or osteoarthritis was not associated with NSAID prescription after discharge., Conclusions: Contraindicated NSAIDs are prescribed to a great extent in elderly patients, despite their greater vulnerability for life-threatening gastrointestinal blood loss. It is remarkable that a history of rheumatoid arthritis or osteoarthritis is no significant determinant for receiving a contraindicated prescription, which suggests that these drugs are mainly prescribed for uncomplicated arthralgia.