Pharmacokinetics of naproxen at two dosage regimens in healthy volunteers.

The pharmacokinetic differences between two dosage regimens of naproxen (1000 mg once daily vs 500 mg twice daily) were studied at steady-state in seven healthy male volunteers. The twice daily regimen resulted in statistically significant higher trough serum levels, larger AUC0----24; also the time span with a concentration over 50 micrograms/ml was longer. The urinary excretion of naproxen metabolites was slightly greater upon once daily dosing. The VDextrap and, to a lesser extent the total body clearance, were larger upon the once daily regimen with a longer t1/2 beta as a consequence. As yet one can only speculate about the therapeutic implications of these findings.