Novel formula for improving the oral bioavailability of paclitaxel using P-glycoprotein inhibitors

Abstract Paclitaxel (PCL), a taxane derivative with potent antimitotic properties, is ubiquitously utilized as a remedy for various cancers. PCL’s therapeutic utility via the oral route is limited by poor water solubility and low permeability, resulting in inadequate bioavailability. This limitation restricts the development of effective oral formulations, particularly for conditions such as gastric cancer. The current research aimed to evaluate the effects of P-glycoprotein (P-gp) inhibitors, specifically piperine (PIP) and silibinin (SBN), on the pharmacokinetic parameters of orally administered PCL. An in-silico drug-protein docking study was performed to evaluate interactions between PCL and selected P-gp inhibitors. PCL was administered orally at a dose of 40 mg/kg, either as a single treatment or in combination with PIP or SBN at 10, 20, and 40 mg/kg. Plasma samples were obtained at predetermined sampling intervals, followed by Liquid chromatography-mass spectrometry (LC-MS) analysis using an H-ESI source. Compared with PCL administered alone, combination treatment significantly enhanced key pharmacokinetic indices, including peak plasma concentration (Cmax) and area under the concentration–time curve (AUC). After administration of PCL with 10 mg/kg of PIP 1.67 and 1.09 fold increases in Cmax and AUC, 20 mg/kg of PIP 1.79 and 1.16 fold increases in Cmax and AUC, and 40 mg/kg of PIP 2.04 and 1.51 fold increases in Cmax and AUC. After administration of PCL with 10 mg/kg of SBN 1.36 and 1.03 fold increases in Cmax and AUC, 20 mg/kg of SBN 1.73 and 1.69 fold increases in Cmax and AUC, and 40 mg/kg of SBN 2.29 and 2.22 fold increases in Cmax and AUC. Additionally, the elimination half-life (t1/2) of PCL was extended, indicating prolonged persistence of the drug in circulation. It can thus be concluded that PCL, along with PIP or SBN, exhibits increased absorption through P-gp modulation. These findings emphasise the promising potential of incorporating such bioenhancers into the development of effective oral PCL formulations to improve cancer therapy. An AGREE score (0.69) indicates the eco-friendliness of the bioanalytical method.