Entrapment of andrographolide in cross-linked alginate pellets: I. Formulation and evaluation of associated release kinetics.

Andrographolide, the 'King of bitters' requires high doses in the form of an extract (33.3%w/w) to be used as a hepatoprotectant. Since a large dose of this herb is known to cause gastric distress, vomiting, loss of appetite and nausea on regurgitation, it was thought of to convert the drug itself into a bitterless micropellet. The technique of ionotropic gelation of sodium alginate with calcium ions with subsequent drug entrapment was employed. The optimization of process parameters like the bore diameter of the needle, % concentration of sodium alginate, method of drying, drying time and temperature, time of contact of the micropellets in calcium chloride solution and concentration of calcium chloride to be used for the gelation were undertaken. The micropellets were finally prepared by adding 2.5%w/v of sodium alginate into a 2%w/v solution of calcium chloride solution using 20-guage flat tip needle and dried using a hot air oven at 60(o)C for 6 hrs. The so formed pellets were completely bitterless and released the andrographolide preferably away from the stomach. Pellets with varied drug: polymer ratio (1:2, 1:1 and 2:1) were prepared accordingly and analyzed for release kinetics. Release studies showed only about 15% release upto 4 hrs in pH 1.2 and pH 4.0 respectively and released the remaining in pH 7.4. The data obtained in the dissolution studies was fitted into various mathematic models defining kinetics of drug release like the zero-order rate equation, first-order rate equation, Hixson-crowell, 2/3rd rule, Korsemeyer-Peppas, Baker-lonsdale, Higuchi, Weibull, Ford and Hopfenberg Equation. The release kinetics of andrographolide from the alginate pellets was found to be best described by the korsemeyer-peppas equation which provided n values ranging from 1.0-1.47 with good linearity of the best-fit line (R(2)=0.9973). In conclusion, andrographolide can be easily converted to bitterless multiple unit dose oral delivery systems with good entrapment efficiency and a maximum release of 86% by utilizing the technique of ionotropic gelation.