Bioavailability of a controlled-release cyclobenzaprine tablet and influence of a high fat meal on bioavailability

Objective: To evaluate the systemic bioavailability of a new controlled release cyclobenzaprine tablet, and the influence of a high fat meal on its bioavailabillty. Subjects, materials and methods: 24 and 12 healthy male subjects were recruited for the bioavailability and influence of diet studies, respectively. Experimental design for both studies was an open randomized, 2-period, single dose, crossover study. In the bioavailability study, each subject received in different occasions, a single oral dose of cyclobenzaprine of immediate (10 mg) or controlled release (20 mg) tablet, followed by a 2-week washout period. In the influence of diet study, the volunteers received the controlled-release tablet concomitantly with a high fat meal or in a state of fasting. Results: In the bioavailability study, plasma cyclobenzaprine profiles were in agreement with a controlled release system. This formulation presented a 92.8% of relative bioavailability (IC 85.5 - 105%) and a significant reduction in C(max) (IC 58 - 65.5%), when compared with equal dose of the immediate release tablet. The presence of food increased AUC (11.6%) and C(max) (48%). For both parameters the calculated 90% confidence interval was not in the bioequivalence interval, 97.4 - 125.8% for AUC and 111.7 - 184.2% for C(max). Conclusions: The controlled release tablet showed a relative bioavailability comparable with equal dose of the immediate release product and produced a significantly lower C(max), as expected in a controlled release formulation. The concomitant administration of the tablet with a high fat meal produced an increase on its bioavailability, mainly in C(max), with no evidence of dose-dumping.