Piperine decreases binding of drugs to human plasma and increases uptake by brain microvascular endothelial cells

We previously reported that piperine, an active alkaloidal principal of black and long peppers, enhances drug bioavailability by inhibiting drug metabolism. Another mechanism influencing drug availability/uptake is its free fraction. Since piperine is highly lipophilic, we hypothesize that it could also interact with drugs through binding displacement and influence their bioavailability. Accordingly, using equilibrium dialysis, we investigated whether piperine alters the binding of model drug ligands, that is flunitrazepam, diazepam, warfarin, salicylic acid, propranolol, lidocaine, and disopyramide to human plasma (n = 4). Since alterations in binding influence drug disposition, we also studied the effects of piperine on the uptake of plasma bound 3 H-propranolol and 14 C-warfarin by cultured bovine brain microvascular endothelial cells (BMECs). Piperine (1-1000 μM) increased the free fraction (fu) of both albumin and alpha-acid glycoprotein bound drugs in a concentration-dependent manner (p < 0.01). Moreover, piperine (10 μM) increased the uptake of 3 H-propranolol and 14 C-warfarin by BMECs (p < 0.01). In conclusion, our findings provide the first evidence that piperine displaces plasma bound drugs from both albumin and alpha-acid glycoprotein and facilitates drug uptake across biological membranes (e.g. BMEC). Moreover, it is feasible that piperine may similarly facilitate the transport of drugs into tissues, in vivo, and alter both pharmacokinetics and pharmacodynamics of administered drugs