ORAL TRAMADOL, A MU-OPIOID AGONIST AND MONOAMINE REUPTAKE-BLOCKER, AND MORPHINE FOR STRONG CANCER-RELATED PAIN

Background: Opioid and spinal monoaminergic agonists have distinct ana lgesic properties, which may potentiate each other. Tramadol has both opioid and monoaminergic agonist actions. This initial study compared the analgesic and toxic effects of tramadol and morphine in patients w ith strong cancer pain. Patients and methods: Pain control and side-ef fects with tramadol and morphine were compared in 20 cancer patients h ospitalised for the treatment of strong pain. Doses of oral solutions of tramadol or morphine were individually titrated in the double-blind , randomized, cross-over study. Crossover was after day 4, the day of statistical evaluation. Results: The mean pain intensity (+/- SD) on a verbal rating scale (0 = none, 4 = unbearable) was similar with morph ine (1.6 +/- 1.2, n = 17) and with tramadol (1.5 +/- 1.3, n = 16) on t he fourth day of dosing. The mean daily doses on day 4 were 101 +/- 58 mg of morphine and 375 +/- 135 mg of tramadol, indicating a relative potency of 4: 1 with oral dosing. The total number of side-effects per person was lower on the fourth day with tramadol (p < 0.05), as was t he severity of nausea (p < 0.05) and constipation decreased with trama dol (p < 0.05). Three patients dropped out of the morphine group due t o side-effects and 4 out of the tramadol group due to inadequate analg esia. Overall, 8 patients (40%) preferred morphine, 3 (15%) favoured t ramadol and 9 (45%) expressed no distinct choice. Nurses rated pain co ntrol better with morphine (p < 0.03), but the tolerability of tramado l was judged superior (p < 0.002). Conclusions: In certain cancer pati ents with strong pain, tramadol achieved good pain control with fewer side-effects than morphine. The non-opioid mode of action may result i n a different spectrum of analgesia and side-effects. Longterm studies are required to confirm this study of brief duration.