A Cochrane review included 51 studies with a total of 5 762 subjects. About half of participants treated with paracetamol at standard doses achieved at least 50% pain relief over 4 to 6 hours, compared with about 20% treated with placebo. NNTs for at least 50% pain relief over 4 to 6 hours following a single dose of paracetamol were as follows: 500 mg NNT 3.5 (2.7 to 4.8); 600 to 650 mg NNT 4.6 (3.9 to 5.5); 975 to 1000 mg NNT 3.6 (3.4 to 4.0). There was no dose response. Sensitivity analysis showed no significant effect of trial size or quality on this outcome. About half of participants needed additional analgesia over 4 to 6 hours, compared with about 70% with placebo. Reported adverse events were mainly mild and transient, and occurred at similar rates with 1000 mg paracetamol and placebo. No serious adverse events were reported. Withdrawals due to adverse events were uncommon and occurred in both paracetamol and placebo treatment arms.