PENTAZOCINE AND PHENAZOCINE: A Double-Blind Comparison of Two Benzomorphan Derivatives in Postoperative Pain

Abstract

The analgesic effeas of intramuscular injections of 30 and 45 mg pentazocine (Win 20, 228) were compared with 2 and 3 mg phenazocine (Narphen) in 128 patients with pain following abdominal surgery. Well-matched pairs of patients were allocated randomly to drugs. Pain was assessed under double-blind conditions, patients' assessments of relief were noted and vital capacity measurements were made. Both drugs were efficient for the relief of postoperative pain and did not cause nausea or vomiting. On average, 38 mg Win 20,228 was analgesically equivalent to 2.6 mg phenazocine. Changes in vital capacity gave a good indication of postoperative pain relief after both upper and lower abdominal operations. These changes were found to be significantly correlated with vital capacity before injection.