HPLC‐UV analysis of bupropion and hydroxybupropion: Application to in vivo pharmacokinetic drug‐drug interaction studies between bupropion and potent CYP2B6 inhibitors

Bupropion is a popular antidepressant that is also prescribed in the management of smoking cessation. In humans, bupropion is predominantly metabolized to its active metabolite hydroxybupropion by CYP2B6. Inhibitors of CYP2B6 have the potential to decrease the clearance of bupropion, leading to adverse drug toxicity. We sought to develop a sensitive HPLC‐UV assay to quantify plasma and brain concentrations of bupropion and hydroxybupropion; and apply the assay to assess in vivo pharmacokinetic (PK) drug‐drug interaction (DDI) studies between bupropion and potent CYP2B6 inhibitors. Tissue extraction followed by HPLC‐UV detected timolol (IS), hydroxybupropion and bupropion at 6, 11 and 36 minutes, respectively. The LOD for both compounds was 6.0 ng/ml, and the intra‐day and inter‐day coefficients of variation was ±12% in plasma and ±15% in whole brain tissue. We then utilized this novel technique to evaluate the PK of bupropion and hydroxybupropion following repeated administration of the known CYP2B6 inhibitor ticlopidine (5 mg/kg daily x 5 days) in CF‐1 mice. Ticlopidine increased the plasma area under the concentration curve ( AUC) of bupropion (2.0‐fold, p< 0.01) and decreased the plasma AUC of hydroxybupropion (1.2‐fold;p< 0.05). In whole brain tissue, ticlopidine increased the AUC of bupropion (1.3‐fold;p> 0.05)and decreased the AUC of hydroxybupropion (2.0‐fold;p< 0.001). In summary, we have developed a sensitive HPLC assay and suitable rodent model to evaluate in vivo PK DDI between bupropion and CYP2B6 inhibitors. Support: Drake Univ COPHS Intramural Research Grants.