Pharmacokinetics of naproxen after oral administration of two tablet formulations in healthy volunteers.

The pharmacokinetics of two naproxen tablet formulations were compared after oral administration. The 250-mg naproxen tablets, tablet I from AFI, Oslo, Norway, and tablet II Naprosyn, Astra-Syntex, were taken by 12 healthy volunteers in a randomized two-period crossover study. Plasma levels of naproxen were measured by a sensitive and specific HPLC method. The data were analyzed by means of two-way analysis of variance to test for significant differences between tablet formulation and differences between the first and second trial periods. Rapid absorption, with most Cmax values from 50-60 micrograms/ml reached within 1.5-3 h, was found for both tablet formulations. No significant difference was found in the rate and extent of absorption between the two formulations: the relative bioavailability of tablet I compared to tablet II was 1.05 +/- 0.21 (mean +/- SD). The naproxen concentration 2 h after ingestion and the Cmax were higher on the second occasion, regardless of preparation, suggesting that the subjects were clinically different on the two occasions.