Metronidazole leads to enhanced uptake of imatinib in brain, liver and kidney without affecting its plasma pharmacokinetics in mice.

Objectives: The pharmacokinetic interaction between metronidazole, an antibiotic-antiparasitic drug used to treat anaerobic bacterial and protozoal infections, and imatinib, a CYP3A4, P-glycoprotein substrate kinase inhibitor anticancer drug, was evaluated.

Methods: Male imprinting control region mice were given 50 mg/kg imatinib PO (control group) or 50 mg/kg imatinib PO, 15 min after 40 mg/kg PO metronidazole (study group). Imatinib plasma, brain, kidney and liver concentrations were measured by HPLC and non-compartmental pharmacokinetic parameters estimated.

Key Findings: Metronidazole coadministration resulted in a double-peak imatinib disposition profile. The maximum concentration (C(max)) decreased by 38%, the area under the curve (AUC(0-∞)) decreased by 14% and the time to C(max) (T(max)) was earlier (50%) in plasma. Apparent volume of distribution (V(SS)/F) and oral clearance (Cl/F) increased by 21% and 17%, respectively. Imatinib tissue penetration was higher after metronidazole coadministration, with 1.7 and 2.1-fold AUC(0-∞) increases in liver and kidney, respectively. Metronidazole increased imatinib's tissue-to-plasma AUC(0-∞) ratio in liver from 2.29 to 4.53 and in kidney from 3.04 to 7.57, suggesting higher uptake efficiency. Brain C(max) was 3.9-fold higher than control and AUC(0-t last) was 2.3-fold greater than plasma (3.5% in control group). No tissue-plasma concentration correlation was found.

Conclusions: Metronidazole slightly decreased imatinib systemic exposure but enhanced liver, kidney and brain penetration, probably due to metronidazole-mediated inhibition of P-glycoprotein and other efflux transporters. The high brain exposure opens possibilities for treatment of glioma and glioblastoma. Renal and hepatic functions may need to be monitored due to potential renal and hepatic toxicity.