Study of Various Formulations for Enhancement of Systemic Bioavailability of Curcumin

Curcumin is a polyphenol derived from the dietary spice, turmeric. It possesses diverse therapeutic effects but it has very poor bioavailability due to poor aqueous solubility and rapid first pass metabolism in the intestinal mucosa and liver. In this work the objective was to develop dosage forms those will avoid the first pass metabolism successfully and extend the bioavailability of curcumin in rabbit. In this direction two sets of formulations (i) Cocoa butter, glycero-gelatin and PEG 6000 based suppositories and (ii) oil and PEG based injections were prepared. In vitro permeation studies were carried out to establish the formulations with suitable release characteristics. It was found that PEG suppositories and PEG injection showed better drug release in vitro. In vivo studies were carried with PEG injection and PEG suppository to determine the pharmacokinetic performance of those formulations. PEG injection was found to show better bioavailability between the two formulations with AUC of 104.8 ? 15.6 (?g h/ml) and mean residence time (MRT) of 2.6 ? 0.5 h. The relative bioavailability of curcumin from PEG injection with respect to PEG suppository was 64.2. With PEG suppositories the glucuronide conjugate form of curcumin (AUC = 25.13 ? 3.57 ?g h/ml) was found to be in greater amount than that of free form (AUC = 16.33 ? 4.5 ?g h/ml) in serum which may be attributed to partial first pass metabolism in the liver when administered through rectal route.