P-Glycoprotein (P-gp), the most extensively studied ATP-binding cassette transporter, functions as a biological barrier by extruding toxic substances and xenobiotics out of cells. Drug efflux pumps such as P-gp play a functional role in determining the pharmacokinetics of drugs administered by oral and parenteral routes. Determining the activity of drug efflux transport proteins has important implications in the identification of substrates and/or inhibitors. The significant role of the small intestine in reducing the oral bioavailability of drugs is due to metabolic enzymes and efflux transporters. The role of cytochrome P-450 3A (CYP3A) and P-gp in intestinal drug disposition has been highlighted. This review examines the structure, localisation and functional role of P-gp, the mechanism of drug efflux and drug-herb interactions.
A buccal patch for systemic administration of carvedilol in the oral cavity has been developed using two different mucoadhesive polymers. The formulations were tested for in vitro drug permeation studies, buccal absorption test, in vitro release studies, moisture absorption studies and in vitro bioadhesion studies. The physicochemical interactions between carvedilol and polymers were investigated by Fourier transform infrared (FTIR) Spectroscopy. According to FTIR the drug did not show any evidence of an interaction with the polymers used and was present in an unchanged state. XRD studies reveal that the drug is in crystalline state in the polymer matrix. The results indicate that suitable bioadhesive buccal patches with desired permeability could be prepared. Bioavailability studies in healthy pigs reveal that carvedilol has got good buccal absorption. The bioavailability of carvedilol from buccal patches has increased 2.29 folds when compared to that of oral solution. The formulation AC5 (HPMC E 15) shows 84.85 + 0.089% release and 38.69 + 6.61% permeated through porcine buccal membrane in 4 hr. The basic pharmacokinetic parameters like the C max , T max and AUC total were calculated and showed statistically significant difference (P<0.05) when given by buccal route compared to that of oral solution.
Aims:The objective of the present study was to develop a bioadhesive bilayered buccal patch of Nimodipine (15 mg) using Eudragit Rs 100 as secondary layer and a primary layer with Hydroxy propyl methyl cellulose and Hydroxy propyl cellulose JF. Methodology: Bilayered buccal patches were prepared by solvent casting technique. The absence of physiochemical interactions between NMDP and the polymer were investigated by differential scanning calorimetry (DSC). Bilayered buccal patches of NMDP were evaluated for in vitro drug permeation through porcine buccal membrane, in vitro drug release, moisture absorption, surface pH, mechanical properties and in vitro bioadhesion.
Results:The results indicated that suitable bioadhesive bilayered buccal patches with desired permeability could be prepared. The bioavailability study was performed in healthy humans in a crossover experimental design. Bioavailability studies revealed that nimodipine possessed good buccal absorption. The relative bioavailability of the optimized buccal patch was found to be 205% in comparison to 30 mg marketed oral tablet. The formulation CC3 showed 68.84 ± 1.4% release and 46.85 ± 5.1% of drug permeated
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