Evaluation of a Potential Clinical Significant Drug-Drug Interaction between Digoxin and Bupropion in Cynomolgus Monkeys.

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A three-period digoxin-bupropion drug-drug interaction study was performed in cynomolgus monkeys to assess the effect of bupropion and its metabolites on digoxin disposition. Monkeys were administered either an i.v. infusion (0.1mg/kg) or an oral dose of digoxin (0.2mg/kg) as control. In single-dosing period, monkeys received an i.v. infusion of bupropion at 1.5mg/kg together with an infusion or oral dosing of digoxin, respectively. During multiple-dosing period, bupropion was orally administered q.d. at 7.72mg/kg for 12-day. Then it was co-administered with an i.v. infusion or oral dosing of digoxin, respectively. Renal expression of OATP4C1 and P-gp was examined. Bupropion significantly increased i.v. digoxin CLrenal0-48h by 1 fold in single-dosing period. But it had no effect on the systemic disposition of digoxin. In multiple-dosing period, bupropion significantly increased oral digoxin CLrenal0-48h, CLtotal0-48h, CLnon-renal0-48h and decreased its plasma exposure. Bupropion and its metabolites did not alter creatinine clearance. OATP4C1 was located at the basolateral membrane of proximal tubule cells, while P-gp was on the apical membrane. The effect of multiple dosing with bupropion on the pharmacokinetics of digoxin is more pronounced. The magnitude of increase in digoxin CLrenal0-48h contributed to the decrease in AUC of digoxin in some extent, but certainly is not the major driving force. The lack of systemic exposure after a single dose but a significant decrease in exposure mediated by an increase in the digoxin CLnon-renal0-48h with repeated dosing is likely to be the more clinically relevant.