Twenty-seven trials were found in 26 reports (one report included 2 trials): 6 trials with head-to-head comparisons of paracetamol-dextropropoxyphene, paracetamol, and placebo (total n=690), 15 trials comparing paracetamol with placebo (n=1,144), and 6 comparing paracetamol plus dextropropoxyphene with placebo (n=397).
Head-to-head comparison: by pooling results from 3 trials (n=202) that provided sufficient data, the difference in pain intensity between paracetamol-dextropropoxyphene and paracetamol alone was 7.3% (95% confidence interval, CI: -0.2, 14.9, p=0.15). According to another 2 trials (n=179), which also provided enough data, the response rate ratio was 1.05 (95% CI: 0.8, 1.3, p>0.05).
Indirect comparison: the mean difference in pain intensity between paracetamol and placebo was 9.4% (95% CI: 6.9, 11.9, p=0.01), and between paracetamol-dextropropoxyphene and placebo, 12.7% (95% CI: 9.2, 16.2, p=0.01) .
Side-effects: compared with placebo, the combination produced more dizziness (RR 3.1, 95% CI: 1.1, 8.9) whereas paracetamol resulted in more drowsiness (RR 1.8, 95% CI: 1.1, 2.9).