Comparative in vitro and in vivo bioavailability of naproxen from tablet and caplet formulations

A 500 mg dose of naproxen in a caplet formulation (product A) or a tablet (Naprosyn 500, product B) was administered to 14 fasting healthy subjects on two separate occasions, separated by a 1-2 week washout period in an open, randomized crossover. Blood samples were drawn periodically and plasma naproxen concentrations measured by HPLC. The median time T-max to reach peak concentration for product A was shorter than that for product B (1.025 h versus 1.5 h) but A and B were similar with respect to median peak plasma concentration C-max (77.9 mg 1-(1) versus 71.4 mg 1-(1)), and average area AUC(0) infinity under the plasma concentration-time curve (1210.2 mg 1-(1) h versus 1211.0 mg 1-(1) h). In vitro parameters (A versus B) of mean dissolution time MDT (5.03 min versus 15.0 min), and time for 70% dissolution T70 (6.67min versus 20.2min), differed significantly