Women on diuretics have a higher risk of hospital admission because of hyponatremia than men.

PURPOSE: Recent studies suggest that women are more susceptible to diuretic-induced hyponatremia resulting in hospital admission than men. The aim of this study was to confirm whether these sex differences in hyponatremia-related hospital admissions in diuretic users remain after adjusting for several confounding variables such as age, dose, and concurrent medication. METHODS: In a case-control design nested in diuretic users, cases of hyponatremia associated hospital admissions between 2005 and 2017 were identified from the PHARMO Data Network. Cases were 1:10 matched to diuretic users as controls. Odds ratios (OR) with 95%CIs were calculated for women versus men and adjusted for potential confounders (age, number of diuretics, other hyponatremia-inducing drugs, chronic disease score) using unconditional logistic regression analysis. A subgroup analysis was performed for specific diuretic groups (thiazides, loop diuretics and aldosterone antagonists). RESULTS: Women had a statistically significantly higher risk of a hospital admission associated with hyponatremia than men while using diuretics (OR 1.86, 95%CI 1.64-2.11). Adjusting for the potential confounders resulted in an increased risk for women compared to men (ORadj 2.65, 95% CI 2.31-3.04). This higher risk in women was also seen in the three subgroup analyses after adjustment. CONCLUSION: Our findings show a higher risk of hyponatremia-related hospital admission in women than men while using diuretics. Further research is needed to understand the underlying mechanism of this sex difference to be able to provide sex-specific recommendations.

Women are started on a lower daily dose of metoprolol than men irrespective of dose recommendations: A potential source of confounding by contraindication in pharmacoepidemiology.

PURPOSE: Current guidelines have no sex-specific dosage advice for metoprolol. To evaluate whether women and men are prescribed the same dose a cohort analysis was performed in the population-based Rotterdam Study (RS). Results were replicated in the Integrated Primary Care Information (IPCI) database of automated general practice data. METHODS: The mean daily starting doses of metoprolol in both sexes were compared with independent-samples t-tests and a linear regression analysis was used to adjust in the RS for co-variables, notably, cardiovascular comorbidity, migraine, age, SBP, DBP, BMI, socioeconomic status, use of other antihypertensive drugs, smoking, and alcohol. In the IPCI-database, adjustment was for age only. RESULTS: The mean daily starting dose was statistically significantly lower in women than in men in both the RS and IPCI database, with a mean difference of 4.8 mg (95%CI -7.8, -1.8) and 4.6 mg (95%CI -5.3,-4.0), respectively. Statistical significance remained after adjustment in both databases. CONCLUSIONS: Women received lower starting doses of metoprolol than men in two independent data collections despite non-sex specific cardiovascular guideline recommendations. This example of real-life pharmacotherapy can lead to a form of confounding by contraindication in pharmacoepidemiology.

Sex-Based Difference in the Effect of Metoprolol on Heart Rate and Bradycardia in a Population-Based Setting.

Background: Metoprolol, a beta-blocker, is used to reduce the heart rate. Although it has been demonstrated that the metoprolol plasma concentration is higher in women than in men, the same dose is recommended. In this study, we investigated whether the metoprolol concentration was associated with a stronger heart-rate reduction and bradycardia in women than in men. Methods: This study is part of the Rotterdam Study (RS), a population-based prospective cohort study. Blood samples from a random subset of 2000 participants were used to assess metoprolol plasma levels. An analysis of heart rate (beats per minute, bpm) and bradycardia (<60 bpm) was performed in metoprolol users with an ECG at the day of blood collection to study sex-specific differences in heart rate and the risk of bradycardia. Results: In total, 40 women and 39 men were included. There was a statistically significant association between metoprolol concentration and heart rate in women (p-value: 0.014) but not in men (p-value: 0.639). Furthermore, women in the highest concentration group had a more than 15-times-higher risk of bradycardia than women in the lowest concentration group (OR = 15.6; 95% CI = 1.1, 217.3); however, this was not seen in men (OR = 1.3; 95% CI = 0.1, 12.4). After adjustment for age, BMI, time between blood sample and ECG, hypertension, myocardial infarction, heart failure, atrial fibrillation, digoxin use, and calcium channel blocker use, the association between concentration and bradycardia in women remained statistically significant. Conclusions: Women, but not men, had a statistically significantly lower heart rate at higher metoprolol plasma concentration and a statistically significantly increased risk of bradycardia.