Pharmacokinetic interaction of single dose of piperine with steady‐state carbamazepine in epilepsy patients

Piperine, the active principle of piper species, is commonly used as a spice and adjuvant in various traditional systems of medicine. It has been known as a bioavailability‐enhancer. The present study aimed at evaluating the effect of piperine on the steady‐state pharmacokinetics of a single dose of carbamazepine in poorly controlled epilepsy patients on carbamazepine monotherapy. Patients (n = 10 each) receiving either 300 mg or 500 mg dose of carbamazepine twice daily were selected. After administration of carbamazepine, venous blood samples were collected at 0, 0.5, 1, 2, 4, 6, 9, 12 h. Subsequently, piperine (20 mg p.o.) was administered along with carbamazepine and samples were collected similarly. The pharmacokinetic parameters were compared by Students t‐test. Piperine significantly increased the mean plasma concentrations of carbamazepine at most of the time points in both dose groups. There was a significant increase in AUC_0‐12hr (p < 0.001), average C_ss (p < 0.001), t_12el (p < 0.05) and a decrease in K_el (p < 0.05), in both the dose groups, whereas changes in K_a and t_12a were not significant. Cmax (p < 0.01) and t_max (p < 0.01) were increased significantly following piperine administration in the 500 mg dose group; however, these parameters were not significant in the lower dose group. Piperine could significantly enhance the oral bioavailability of carbamazepine, possibly by decreasing the elimination and/or by increasing its absorption. Copyright © 2009 John Wiley & Sons, Ltd.