Food–drug interactions: effect of capsaicin on the pharmacokinetics of galantamine in rats

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide, CAP) is a naturally occurring alkaloid extracted from the fruit of Capsicum plant family. It represents an important ingredient in spicy foods consumed throughout the world. However, little is known about the metabolic interactions between CAP and clinically used drugs. This study attempted to investigate the effect of CAP on the pharmacokinetics of galantamine, a competitive and reversible cholinesterase inhibitor. CAP, dexamethasone or sodium salt of carboxymethyl cellulose (CMC-Na) was given to rats for seven consecutive days and on the seventh day galantamine (10 mg/kg) was administered orally. Dexamethasone was used as a CYP inducer and CMC-Na was used as a vehicle. The results showed that the pretreatment of rats with CAP resulted in a decrease in the AUC(0-∞) of galantamine of about 49.70% (p < 0.01) compared with the control group. After oral administration of galantamine (10 mg/kg), the apparent oral clearance of galantamine was raised by 2.05-fold by pretreatment with CAP (p < 0.05). These results demonstrate that the chronic ingestion of high doses of CAP will decrease the bioavailability of galantamine to a significant extent in rats.