Systematic overview of co-proxamol to assess analgesic effects of addition of dextropropoxyphene to paracetamol

Objective: To evaluate the comparative efficacy and tolerability of paracetamol-dextropropoxyphene combination and paracetamol through a systematic overview of randomised controlled trials. Design: Systematic retrieval of trials of paracetamol-dextropropoxyphene, paracetamol, and placebo to allow pooling of results from head to head comparison trials and single active placebo controlled trials. Subjects: 2231 patients with postsurgical pain, arthritis, and musculoskeletal pain reported in 26 randomised controlled trials. Main outcome measures: Sum of difference in pain intensity; response rate ratio and difference in response rate with response defined as moderate to excellent pain relief; and rate ratio and rate difference of side effects. Results: The difference in pain intensity between paracetamol-dextropropoxyphene and paracetamol was 7.3% (95% confidence interval -0.2 to 14.9). The response rate ratio for the combination and paracetamol was 1.05 (0.8 to 1.3) on the basis of the head to head trials. Indirect comparisons produced quantitatively consistent results. Compared with placebo, the combination produced more dizziness (3.1; 1.1 to 8.9) whereas paracetamol resulted in more drowsiness (1.8; 1.1 to 2.9). Conclusion: On the basis of data on analgesic efficacy and acute safely in both head to head and indirect comparisons, there is little objective evidence to support prescribing a combination of paracetamol and dextropropoxyphene in preference to paracetamol alone in moderate pain such as that after surgery.