Formulation and in vitro evaluation of theophylline-Eudragit® sustained-release tablets

Abstract

Tablets containing theophylline (66.67%) based on a Eudragit® RS 30D and NE 30D matrices containing 10% to 30% of either of the polymer were produced by compression method. The influence of the different proportions of methacrylic esters, the use of lactose and tribasic calcium phosphate as diluents and also the effects of the addition of magnesium stearate as a hydrophobic agent lubricant on the theophylline release, were studied. Physicochemical analyses and drug content was evaluated. In vitro drug release studies were carried out in simulated gastric fluid without pepsin (pH1.2) and simulated intestinal fluid without pancreatin (pH7.5). A relatively prolonged release of theophylline from the polymer matrices for a 7 hr-release period was detected. Magnesium stearate at 0.5% and Eudragit® NE 30D at 10% was considered a better sustained-release matrix compressed theophylline tablets comparing with Eudragit® RS 30D in the same conditions (USP). Results from physicochemical analyses were in accordance with specifications. The release patterns were analyzed from the viewpoint of square-root of time and as a first-order, zero-order kinetics, and Higuchi. Additionally, half-life of release (Td50%) and dissolution rates (kd) were calculated. Higuchi was the model that better fitted theophylline kinetic, and diffusion controlled was involved.