Enhancement Of Oral Bioavailability Of Methotrexate With The Help Of Natural Bioenhancer

Abstract

The aim of this study was to enhance the oral bioavailability of methotrexate with the help of natural bioenhancer. Methotrexate is a specific substrate of P-gp mediated efflux, BCRP and ABC transporters. Several studies have been demonstrated that P-gp over expression leads to MTX-resistance. Treatment with P-gp inhibitor has been shown significant improvement in oral bioavailability. Piperine is an isoflavonoid and is supposed to be an inhibitor of ABC transporters, P-gp efflux inhibitor and BCRP. The purpose of this study is to evaluate the effect of orally administered piperine on the pharmacokinetics of methotrexate in rabbits. Rabbits were weight around 3.0 kg, was randomly assigned to equal groups (3 rabbits each). The present protocol consists of single dose of methotrexate (0.5mg/kg b.wt) (Group 1), single oral dose of piperine in group (2, 3, and 4) (0.5mg/kg, 5mg/kg, 50mg/kg) with single oral dose of methotrexate in each group. Blood samples were collected from left or right marginal vein at different time intervals of 0, 0.25 (15 minutes), 0.5 (30 minutes), 1, 2, 4, 8, 10, 12, 15, 18 and 24 hours after oral administration and plasma was separated for HPLC analysis. The plasma concentration-data were analyzed by non-compartmental pharmacokinetic analysis. In the presence of piperine was significantly (p<0.05) increased the Area under plasma concentration –time curve (AUC0-t) in all the piperine treated groups (p<0.05, 1.28, 2.02, 2.57) times was significantly increased in AUC0-t of group 2, group 3 and group 4 as compared to group 1. The piperine also increase the peak concentration (Cmax) of methotrexate significantly (p<0.05 by 0.5 mg/kg, 1.486 times; p<0.05 by 5mg/kg, 1.99 times; p<0.05 by 50mg/kg, 2.5 times higher) than control group. Piperine can significantly (p<0.05) increase the elimination half-life (t1/2) of the group 3 as compared to the control group. Piperine can also significantly declined the elimination rate constant (ꞵ) of methotrexate-piperine (p<0.05 at 0.5mg/kg; 5mg/kg and 50mg/kg, 0.065, 0.619, 0.583 times declined respectively. The mean residual time (MRT) of methotrexate was significantly increased (p<0.05 by 0.5mg/kg, 5mg/kg, 50mg/kg, 1.31, 1.38, 1.45 times respectively. Total plasma clearance (CLB) was decreased significantly with piperine of all treated groups when compared with control group. So, it can be concluded that from this study, when methotrexate administered with piperine at different doses, has been shown higher t1/2, AUC, Cmax, MRT values and lower clearance values and elimination rate constant (ꞵ). The increased Cmax value of methotrexate co-administered with piperine in rabbits could be attributed to the ability of piperine to inhibit the hepatic metabolism, increase the intestinal absorption and to inhibit the P-gp mediated drug efflux during intestinal absorption.