Paracetamol versus placebo: 31 trials (1,338 patients given paracetamol, 1,177 given placebo), of which 19 trials investigated oral surgery, 8 postsurgical and 4 postpartum pain.
Paracetamol plus codeine versus placebo: 19 trials (631 patients given paracetamol plus codeine, 573 given placebo), of which 14 trials investigated oral surgery and 5 postsurgical pain.
Paracetamol plus codeine versus paracetamol: 13 trials (435 patients given paracetamol plus codeine, 439 given paracetamol alone), of which 10 trials investigated oral surgery and 3 postsurgical pain.
Paracetamol versus placebo (all conditions). 500 mg paracetamol versus placebo: the RR and NNT were 1.6 (95% CI: 0.8, 3.5) and 3.6 (95% CI: 2.5, 6.5), respectively. 600 or 650 mg paracetamol versus placebo: the RR and NNT were 1.7 (95% CI: 1.3, 2.2) and 5.0 (95% CI: 4.1, 6.9), respectively. 1000 mg paracetamol versus placebo: the RR and NNT were 2.5 (95% CI: 1.9, 3.3) and 3.6 (95% CI: 3.0, 4.4), respectively.
Paracetamol plus codeine versus placebo. 300 mg paracetamol plus 30mg codeine versus placebo: the RR and NNT were 3.0 (95% CI: 1.8, 5.0) and 5.3 (95% CI: 3.8, 8.0), respectively. 600 or 650 mg paracetamol plus 60mg codeine versus placebo: the RR and NNT were 2.6 (95% CI: 2.1, 3.2) and 3.1 (95% CI: 2.6, 3.8), respectively. 1000 mg paracetamol plus 60 mg codeine versus placebo: the RR and NNT were 2.8 (95% CI: 1.2, 6.8) and 2.4 (95% CI: 1.5, 5.7), respectively.
Paracetamol plus codeine versus paracetamol. 300 mg paracetamol plus 30 mg codeine versus same dose paracetamol alone: the RR and NNT were 1.2 (95% CI: 1.0, 1.4) and 10 (95% CI: 5.9, 43), respectively. 600 or 650mg paracetamol plus 60 mg codeine versus same dose paracetamol alone: the RR and NNT were 1.3 (95% CI: 1.1, 1.5) and 6.7 (95% CI: 3.4, 174), respectively. 1000 mg paracetamol plus 60 mg codeine versus same dose paracetamol alone: the RR and NNT were 1.2 (95% CI: 1.0, 1.4) and 9.1 (95% CI: 5.8, 24), respectively.
The 18 trials combined for all conditions for 600 or 650 mg paracetamol versus placebo were found to be heterogeneous, as were the 3 trials of postpartum pain comparing 1000 mg paracetamol versus placebo. All other combinations of trials were homogeneous.