Objective: To investigate the effects of the clinical dose of clarithromycin, a substrate of P-glycoprotein (P-gp), on P-gp function using positron emission tomography (PET) with [11C]verapamil.
Methods: Two PET scanning with [11C]verapamil were performed before and after administration of 400 mg/day of clarithromycin on each of four healthy male subjects. The rate constant of transfer from plasma to brain (K1) was estimated by integration plot method.
Results: K1 values of [11C]verapamil before administration of clarithromycin were 0.042-0.070 mL/cm3/min (0.054 ± 0.012) and those after administration were 0.037-0.066 mL/cm3/min (0.055 ± 0.013). No significant change in K1 values of [11C]verapamil was observed between before and after administration of clarithromycin (P = 0.85).
Conclusion: K1 values of [11C]verapamil were not changed by clinical dose administration of clarithromycin, suggesting that a clinical dose of clarithromycin does not affect P-gp function at the blood-brain barrier.