Zero-order release of theophylline from a core-in-cup tablet in sequenced simulated gastric and intestinal fluid

Core-in-cup tablets containing theophylline were evaluated for their dissolution characteristics in sequenced simulated gastric fluid (SGF) followed by simulated intestinal fluid (SIF). Core-in-cup tablets containing 10% w/w, 20% w/w, and 30% w/w acacia as binder were evaluated for their effects on the time course of release of theophylline. This was done to optimize a formula that could release theophylline at a zero-order rate of release for 8-16 hr in simulated gastrointestinal fluids. Theophylline was released and dissolved from the core-in-cup tablets at a rate that is more consistent with a zero-order dissolution rate than a first-order dissolution rate in both SIG and SIF. The dissolution rates of theophylline from the 10%, 20%, and 30% acacia core-in-cup tablets were 0.87 mg/min, 0.53 mg/min, and 0.27 mg/min, respectively in SGF, and 0.61 mg/min, 0.30 mg/min, and 0.20 mg/min, respectively in SIF. The results indicate that a concentration of 32% w/w acacia in the core tablet will release theophylline at a rate of 0.14 mg/min in SGF for 2 hr followed by SIF for 10 hr.