Naproxen sodium, aspirin, and placebo in primary dysmenorrhea. Reduction of pain and blood levels of prostaglandin F2-alpha metabolite.

In a double-blind, crossover study of 32 women with primary dysmenorrhea, the analgesic efficacy of naproxen sodium was compared to that of aspirin and placebo. The treatment started 1 to 5 days before the onset of menses and continued for 3 to 5 days. At the same time, a radioimmunoassay established concentrations of 13,14-dihydro-15-keto-prostaglandin F2-alpha, a prostaglandin F2-alpha metabolite (PGF-M) in blood samples obtained from before the treatment and on the first day of menses. In affording pain relief, naproxen sodium was superior to aspirin (p = 0.02) and placebo (p = 0.002); however, aspirin was not superior to placebo (p = 0.05). During naproxen sodium treatment, the patients' daily activities were less impaired than during both the aspirin and the placebo treatment courses. During naproxen sodium treatment, the mean blood PGF-M levels decreased by 73.5%, from a mean of 50.5 to 13.4 pg/ml; during aspirin treatment they decreased by 31.2%, from a mean of 44.2 to 30.4 pg/ml; during placebo treatment, an increase of 13.6% was observed, from a mean of 46.3 to 52.6 pg/ml. The PGF-M decrease during the naproxen sodium treatment was significantly more prominent than that during both aspirin and placebo treatments (p = 0.0001). Changes caused by aspirin treatment were significantly different from those occurring during the placebo treatment (p = 0.001). The study confirms that at the doses utilized in this study the analgesic properties of naproxen sodium are superior to those of the more conventional prostaglandin synthetase inhibitor, aspirin, and that pain relief is related to the inhibition of prostaglandin synthesis.