We explored the bioavailability and kinetics of naproxen (N) in 12 healthy volunteers treated orally with single doses of 500 mg and retreated after a washout period with the same dose of N plus sulglycotide (S) 200 mg. Naproxen blood levels were measured by high-performance liquid chromatography (HPLC) in samples collected at 0.5, 1, 2, 4, 8, 12, and 24 h of dosing with N or with N + S. No statistically significant difference in terms of naproxen blood levels emerged as the product was administered alone or concurrently with sulglycotide. Peak plasma concentrations and AUC values were 71 +/- 3.16 micrograms/ml and 685 +/- 27 micrograms/ml/h, respectively for N alone, and 72.5 +/- 2.85 micrograms/ml and 651 +/- 28 micrograms/ml/h, respectively for N + S. The difference was not significant. Similarly, the kinetic behavior of naproxen was not modified by the simultaneous presence of sulglycotide, as shown by the t1/2 beta-values obtained with N alone (8.39 +/- 0.31 h) and with N + S (7.93 +/- 0.30 h), and likewise by the distribution volumes at equilibrium (7.63 +/- 0.42 and 7.9 +/- 0.38, respectively), Cmax (63.3 +/- 2.86 and 60.4 +/- 2.9 micrograms/ml, respectively) and tmax (0.95 +/- 0.06 and 1.10 +/- 0.10 h, respectively). From these findings it seems legitimate to claim that sulglycotide can be administered concurrently with naproxen to prevent possible gastric injury by the anti-inflammatory agent thanks to its wellknown antiulcer and cytoprotective activity on the gastric mucosa, without any undue interference with the absorption (hence effectiveness) of naproxen.