1. ¹Faculty of Medicine of Ribeirão Preto, Rua-Campos Sales, 330, Apto. 44, University of São Paulo, São Paulo 14015-110, Brazil
2. ²Pharmaceutical Technology of the Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Brazil

Correspondence: Dr GR Lauretti, E-mail: grlauret@fmrp.usp.br

Received 17 January 2003; Revised 30 August 2003; Accepted 7 September 2003.

Abstract

The antinociceptive effect of morphine and oxycodone is mediated preferentially at and receptors, respectively. The aim of this study was to evaluate the analgesic profile of the combination of morphine and oxycodone in cancer pain, compared to the standard administration of morphine alone. Controlled-release formulations of oxycodone (CRO) and morphine (CRM) were compared in 26 patients. The study started with an open-label, randomised titration phase to achieve stable pain control for 7 days, followed by a double-blind, randomised crossover phase in two periods, 14 days each. At any point, patients were allowed to use oral immediate-release morphine (IRM) as needed, in order to keep visual analogue scale 4. Pain, satisfaction, adverse effects and number of daily rescue morphine tablets were assessed. A total of 22 patients were evaluated. The weekly upload consumption ratio in morphine/oxycodone was 1 : 1.8 (1.80, 1.83, 1.76, 1.84). The weekly IRM consumption was higher in patients having CRM compared to patients having CRO (ratio morphine/oxycodone: 1.6, 1.6, 1.6, 1.7) (P<0.05). Patients receiving oxycodone complained of less nausea and vomiting. The rescue morphine analgesic consumption was 38% higher in patients receiving only morphine, compared to patients receiving both morphine and oxycodone. The results suggest that the combination of morphine/oxycodone (opioids with differential preferential sites of action) can be a useful alternative to morphine alone, resulting in a better analgesia profile and less emesis.