Effects of sertraline on the pharmacokinetics of bupropion and its major metabolite, hydroxybupropion, in mice

Sertraline potently inhibits cytochrome P450 2B6 (CYP2B6) in vitro. Bupropion is commonly co-prescribed with sertraline and is exclusively metabolized by CYP2B6 to its major active metabolite hydroxybupropion. Putatively the co-administration of bupropion and sertraline could lead to a significant pharmacokinetic drug-drug interaction. The aim of this study was to evaluate a possible drug interaction between these drugs in mice. To study this male CF-1 mice were administered sertraline 5 mg/kg once daily for 6 days, followed by a single dose of bupropion 50 mg/kg on the seventh study day. Plasma and brain samples were collected post-bupropion dose for measurement of bupropion and hydroxybupropion levels on HPLC. Pharmacokinetic parameters for bupropion and hydroxybupropion were calculated using noncompartmental analysis and the variance in AUC of each was computed using Bailer's analysis. We found that mice pretreated with sertraline exhibited a small elevation in bupropion metabolism. This was substantiated by Bailer's analysis which indicated that in the presence of sertraline, both plasma and brain bupropion exposure were significantly (p < 0.05) decreased, while plasma hydroxybupropion exposure was significantly (p < 0.05) increased. Also the plasma hydroxybupropion-to-bupropion ratio of AUC was increased by 27% in sertraline treated mice, indicative of increased CYP2B activity. This is the first study, to our knowledge, that reports a mild pharmacokinetic drug-drug interaction between bupropion and sertraline in mice. However, it is unknown whether these quantitative changes in enzyme activity and consequent drug exposure would equate to significant pharmacodynamic changes (e.g., perturbations in brain neurotransmitter levels) observed in the clinic.