Pharmacokinetic profile of extended-release versus immediate-release oral naproxen sodium after single and multiple dosing under fed and fasting conditions: two randomized, open-label trials

Purpose: Extended-release (ER) naproxen sodium provides pain relief for up to 24 hours with a single dose (660 mg/day). Its pharmacokinetic profile after single and multiple dosing was compared to immediate release (IR) naproxen sodium in two randomized, open-label, crossover studies, under fasting and fed conditions. Methods: Eligible healthy subjects were randomized to ER naproxen sodium 660-mg tablet once daily or IR naproxen sodium 220-mg tablet twice daily (440 mg initially, followed by 220 mg 12 hours later). Primary variables: pharmacokinetic parameters after singleday-administration (day 1) and at steady state after multiple-day administration (day 6). Results: Total exposure was comparable for both treatments under fasting and fed conditions. After fasting: peak naproxen concentrations were slightly lower with ER naproxen sodium than with IR naproxen sodium but were reached at a similar time. Fed conditions: mean peak concentrations were comparable but reached after a longer time with ER vs. IR naproxen sodium. ER naproxen sodium was well tolerated, with a similar safety profile to IR naproxen-sodium. Conclusions: The total exposure of ER naproxen sodium (660 mg) is comparable to IR naproxen-sodium (220 mg) when-administered at the maximum over the counter (OTC) dose of 660-mg daily dose on a single day and over multiple days. The rate of-absorption is-delayed under fed conditions.