A double-blind, placebo-controlled, parallel group study was performed to compare the analgesic efficacy of diclofenac potassium (25, 50, or 100 mg) with that of aspirin (650 mg), or placebo. Two hundred fifty-five inpatients with severe postepisiotomy pain were randomly assigned to receive a single oral dose of one of the four active treatments or placebo. Analgesia was assessed over an 8-hour period. Treatments were compared on the basis of standard scales for pain intensity and relief and a number of derived variables based on these data, as well as two global ratings of the study medication. All active treatments were effective analgesics statistically superior to placebo for many hourly and summary measures, including the global ratings. Diclofenac potassium (50 and 100 mg) was statistically significantly superior to aspirin at half-hour and for many other hourly scores from hour 3 on. The 4− and 8-hour sum of the pain intensity difference and total pain relief scores reflected the superiority of diclofenac potassium to aspirin. In addition, the 100-mg dose was significantly more efficacious than the 25-mg dose of diclofenac potassium. The probability of obtaining onset was significantly better for all active treatments than for placebo; however, the median onset times were similar for all treatments. The duration of effect, as measured by mean pain intensity difference and relief scores, was better for diclofenac potassium than aspirin, and these differences were significant for the 50− and 100-mg doses. The probability of pain returning to baseline was significantly less for the diclofenac groups than for placebo or aspirin groups. In addition, significantly fewer patients treated with diclofenac (25, 50, or 100 mg) or aspirin (650 mg) required remedication during the 8-hour study period as compared with those treated with placebo. Diclofenac potassium is an effective analgesic in the range of aspirin (650 mg) at the 25-mg dose and superior in efficacy and longer lasting than aspirin at the 50− and 100-mg doses. The onset of analgesia was similar for aspirin and diclofenac potassium.
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