Naproxen, aspirin, and codeine in postpartum uterine pain.

The analgesic efficacy of oral naproxen and its sodium salt was compared with that of aspirin and codeine in two separate trials involving 140 and 90 patients, respectively, with postpartum uterine pain in a single-dose, parallel, stratified, randomized, placebo-controlled, double-blind design. With 300 or 600 mg naproxen and with 275 mg naproxen sodium, significant analgesia, measured subjectively by pain intensity differences (PID), was prolonged at least 7 or 8 hr; onset tended to be delayed 2 hr or more. With 650 mg aspirin analgesia began within 1 hr and continued until the fifth hour, while with 60 mg codeine responses were indistinguishable from placebo responses throughout the 8-hr time course. Although time-effect patterns with naproxen sodium and aspirin were different, summed analgesic effects (SPID) showed equal efficacy and superiority over placebo (p less than 0.005). With each of the 2 doses of naproxen, SPID separation from placebo was comparable to that above (p less than 0.02 and 0.005, respectively), but analgesic dose response, though measurable, was not significant. Side effects were not significant with any of the treatments. It appears that naproxen and naproxen sodium are analgesics with efficacy equal to aspirin and may prove to be rational substitutes for currently available analgesics in some painful states in which longer pain relief would be desireable.