title: Effect of amiodarone on the serum concentration/dose ratio of metoprolol in patients with cardiac arrhythmia.
abstract: Amiodarone has pharmacokinetic interactions with a number of therapeutic drugs, including warfarin, phenytoin, flecainide, and cyclosporine. Metoprolol is mainly metabolized by CYP2D6, and desethylamiodarone, a metabolite of amiodarone, has a markedly greater inhibitory effect on CYP2D6 than amiodarone. Therefore, the goal of this study was to evaluate the effect of amiodarone and desethylamiodarone on the serum concentration/dose ratio (C/D) of metoprolol in 120 inpatients with cardiac arrhythmias that received either metoprolol and amiodarone (MET+AMD group, n=30) or metoprolol alone (MET group, n=90). The ratio of administered metoprolol was compared between the MET and the MET+AMD groups. The dose of metoprolol and patient age were significantly higher in the MET group when compared with the MET+AMD group (1.00+/-0.480 versus 0.767+/-0.418 mg/kg/day, p<0.050; 68.6+/-10.6 versus 57.6+/-14.1 years, p<0.001, respectively), but the C/D ratio was significantly lower in the MET group than in the MET+AMD group (90.8+/-64.0 versus 136+/-97.8, p<0.01). Furthermore, a significant correlation was found between the C/D ratio and desethylamiodarone concentration (n=30, r=0.371, p<0.01). The results suggest that there is a significant interaction between amiodarone and metoprolol via desethylamiodarone-induced inhibition of CYP2D6. Therefore, careful monitoring of metoprolol concentrations/bioactivity of CYP2D6 is required in the context of co-administration of amiodarone and metoprolol.
authors.affiliation: Department of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Fukumoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Kanako
authors.initials: K
authors.lastname: Tachibana
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kato
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Kazuo
authors.initials: K
authors.lastname: Komamura
authors.forename: Shiro
authors.initials: S
authors.lastname: Kamakura
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kitakaze
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ueno
mesh_terms: D000328:Adult; D000368:Aged; D000638:Amiodarone / Q000031:analogs & derivatives / Q000097:blood / Q000494:pharmacology* / Q000627:therapeutic use; D000889:Anti-Arrhythmia Agents / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D001145:Arrhythmias, Cardiac / Q000188:drug therapy*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008875:Middle Aged
chemical_list: D000889:Anti-Arrhythmia Agents; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D019389:Cytochrome P-450 CYP2D6; D008790:Metoprolol; C036116:desethylamiodarone; D000638:Amiodarone