title: Toward optimal treatment in women: the effect of sex on metoprolol-diphenhydramine interaction.
abstract: The objective of this study was to determine if sex influences the pharmacokinetics and hemodynamics of the CYP2D6 substrate metoprolol and its interaction with diphenhydramine (CYP2D6 inhibitor) in healthy young participants with high (extensive metabolizer [EM]) or low (poor metabolizer [PM]) CYP2D6 activities. A prespecified comparative analysis of data from 2 sequential clinical trials that included 16 EM and 4 PM women and 10 EM and 6 PM men was performed. The participants in the 2 trials were administered a single oral dose of 100 mg metoprolol in the presence of steady-state diphenhydramine or placebo. Serial plasma and urine samples were obtained for 48 hours, and hemodynamic data was obtained for 12 hours after metoprolol. In the placebo arm, EM and PM women had 62% and 59% higher S-metoprolol AUC(0-infinity) and 26% and 71% lower CL/F, respectively, compared to men with the same phenotype (all Ps < .05 women compared to men). These differences dissipated on body weight (WT) correction. Women (especially PMs) experienced greater negative chronotropic effects of metoprolol than men (P < .0001 women compared to men). Diphenhydramine coadministration increased S-metoprolol AUC by 84% in EM women and 45% in EM men (P < .009 women compared to men). In the diphenhydramine arm, sex differences in pharmacokinetics persisted even after WT correction, resulting in greater negative chronotropic effects in women (all Ps < .05 women compared to men). Metoprolol dose should be adjusted for body weight, particularly in women. Coadministration of a CYP2D6 inhibitor such as diphenhydramine, by a patient at similar doses in the 2 sexes, could result in a greater inhibition of clearance of CYP2D6 substrates with a resulting higher risk of pronounced pharmacological and adverse effects in women compared to men.
authors: Quebec Heart and Lung Institute, Ste-Foy, Quebec, Canada. ashish.sharma@bc.boehringer-ingelheim.com
authors: Ashish
authors: A
authors: Sharma
authors: Philippe
authors: P
authors: Pibarot
authors: Sylvie
authors: S
authors: Pilote
authors: Jean G
authors: JG
authors: Dumesnil
authors: Marie
authors: M
authors: Arsenault
authors: Pierre Maxime
authors: PM
authors: Bélanger
authors: Bernd
authors: B
authors: Meibohm
authors: Bettina A
authors: BA
authors: Hamelin
mesh_terms: D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000493:pharmacokinetics; D018592:Cross-Over Studies; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004155:Diphenhydramine / Q000494:pharmacology*; D004311:Double-Blind Method; D004347:Drug Interactions; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000493:pharmacokinetics*; D010597:Pharmacogenetics; D012737:Sex Factors; D055815:Young Adult
chemical_list: D000889:Anti-Arrhythmia Agents; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D006634:Histamine H1 Antagonists; D004155:Diphenhydramine; D019389:Cytochrome P-450 CYP2D6; D008790:Metoprolol