Paracetamol is the most commonly prescribed
analgesic for the treatment of
acute pain. The efficacy and safety of i.v. formulations of
paracetamol is unclear. We performed a systematic search (multiple databases, bibliographies, any language, to May 2010) for single-dose, randomized, controlled clinical trials of
propacetamol or i.v.
paracetamol for
acute postoperative pain in adults or children. Thirty-six studies involving 3896 patients were included. For the primary outcome, 37% of patients (240/367) receiving
propacetamol or i.v.
paracetamol experienced at least 50%
pain relief over 4 h compared with 16% (68/527) receiving placebo (number needed to treat=4.0; 95% confidence interval, 3.5-4.8). The proportion of patients in
propacetamol or i.v.
paracetamol groups experiencing at least 50%
pain relief diminished over 6 h. Patients receiving
propacetamol or
paracetamol required 30% less
opioid over 4 h and 16% less
opioid over 6 h than those receiving placebo. However, this did not translate to a reduction in
opioid-induced adverse events (AEs). Similar comparisons between
propacetamol or i.v.
paracetamol and active comparators were either not statistically significant, not clinically significant, or both. AEs occurred at similar rates with
propacetamol or i.v.
paracetamol and placebo. However,
pain on infusion occurred more frequently in those receiving
propacetamol compared with placebo (23% vs 1%). A single dose of either
propacetamol or i.v.
paracetamol provides around 4 h of effective
analgesia for about 37% of patients with
acute postoperative pain. Both formulations are associated with few AEs, although patients receiving
propacetamol have a higher incidence of
pain on infusion.