Evaluation of felodipine as a potential perpetrator of pharmacokinetic drug-drug interactions

Objective To evaluate felodipine as a potential perpetrator of pharmacokinetic drug-drug interactions (PK-DDIs) involving cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp). Methods Felodipine extended-release 10 mg was administered daily to six healthy subjects for 7 days (days 1–7). Subjects were administered a modified Inje cocktail comprising the selective probe substrates caffeine 100 mg (CYP1A2), losartan 25 mg (CYP2C9), omeprazole 20 mg (CYP2C19), dextromethorphan 30 mg (CYP2D6), midazolam 2 mg (CYP3A) and digoxin 250 μg (P-gp) on day 0 (prior to felodipine exposure) and day 7 (after felodipine exposure). Plasma samples were collected over 24 h and drug concentrations measured by UPLC-MS/MS. Results The geometric means of the area under the plasma concentration–time curve ratios (probe AUC after felodipine exposure/probe AUC prior to felodipine exposure) and 95 % confidence intervals for each probe were: caffeine 0.91 (0.64–1.30), losartan 1.05 (0.95–1.15), omeprazole 1.17 (0.78–1.76), dextromethorphan 1.46 (1.00–2.12), midazolam 1.23 (0.99–1.52) and digoxin 1.01 (0.89–1.15). Conclusion Felodipine may be a weak in vivo inhibitor of CYP3A and CYP2D6 but is unlikely to act as a significant perpetrator of PK-DDIs.