| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2479517 | Drug Metabolism and Pharmacokinetics | 2006 | 5 Pages |
Summary: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.
