Comparative bioavailability of two oral suspensions of naproxen sodium

The bioavailability of naproxen sodium (CAS 26159-34-2) after administration of two oral suspensions, reference or test (Pactens®), was compared in 24 healthy subjects. The volunteers received an oral dose of 250 mg (10 ml) in two separate sessions under fasting conditions according to a randomized cross-over design and blood samples were obtained at selected times for a period of 72 h. Plasma samples were analyzed by a high-performance liquid chromatographic method for determination of naproxen. Individual plasma concentration against time curves were constructed and pharmacokinetic parameters were obtained by non-compartmental techniques. The parameters obtained (mean ± S.E.M.) were: C_max 43.93 ± 1.83 and 44.91 ± 2.15 μg/ml, t_max 2.38 ± 0.21 and 1.83 ± 0.19 h, AUC_{72 h} 721.73 ± 18.47 and 722.55 ± 19.07 μg · h/ml for reference and test formulations, respectively. Maximal concentration, AUC_{72 h} and AUC_∞, were log transformed and compared by analysis of variance and ratios; in addition, 90% confidence limits were obtained. As confidence limits were included in the 80-125% range and the probability of exceeding these intervals was always lower than 0.05, it is concluded that the formulations tested are bioequivalent.