Adjunct dipyrone in association with oral morphine for cancer-related pain: the sooner the better

Abstract

Introduction: Adjunct nonopioid analgesics may improve pain control in patients with cancer needing morphine or its derivates. Dipyrone is a cheap nonopioid analgesic widely used in many countries.

Objective: The objective of the study was to evaluate, whenever morphine was started, if associating dipyrone with it would improve pain control and if this effect was time dependent.

Materials and methods: This is a double-blind placebo-controlled randomized crossover study. Thirty-four ambulatory cancer patients experiencing cancer-related pain for which oral morphine was to be started at the dose of 10 mg orally (PO) every 4 h were randomized to take either dipyrone 500 mg PO every 6 h or placebo. After 48 h, patients would be switched from dipyrone to placebo and vice versa. Pain was the primary outcome and was measured using a visual analogue scale before starting medications, at 48 and 96 h.

Results: We randomized 16 patients to start with placebo (group 1) and 18 with dipyrone (group 2). Pain scores for groups 1 and 2 were at baseline: 7.31 +/- 0.29 vs 6.88 +/- 0.28 (p = 0.3), at 48 h: 7.06 +/- 0.32 vs 5.5 +/- 0.31 (p = 0.001), and at 96 h: 3.18 +/- 0.39 vs 1.94 +/- 0.37 (p = 0.03). Both groups had significant improvements in pain scores after introducing dipyrone (p < 0.001, for both). Main toxicities were nausea, vomiting, epigastric pain, and myalgias. Twenty-eight patients chose dipyrone, four placebo, and two were indifferent.

Conclusions: We conclude that dipyrone adds significantly to the analgesic effect of morphine and, when given at the time of starting morphine, results in better pain scores even after dipyrone is discontinued.