Eighty-five studies were included in the review. Fifty-four studies (n=7,603 participants) assessed the effects of treatments on pain (36 in adults and 18 in children). Thirty-five studies (n=3,985) assessed the effects of treatments on fever (five in adults and 30 in children). Sixty-six studies (n not reported) assessed the adverse effects of treatments, 35 in adults and 31 in children.
Pain in adults: Twenty-six studies concluded that ibuprofen was superior to acetaminophen and 10 reported no significant difference between treatments. In the meta-analysis of RCTs, ibuprofen was associated with a significantly lower pain score than acetaminophen at two hours post dose (SMD 0.69, 95% CI 0.57 to 0.81; nine studies), which corresponded to a medium effect size using Cohen's rule of thumb.
Pain in children: Six studies concluded that ibuprofen was superior to acetaminophen, 11 studies reported no significant difference between treatments and one study found a significant difference for ibuprofen only on the day of surgery and not at later time points. In the meta-analysis of RCTs, ibuprofen was associated with a significantly lower pain score than acetaminophen at two hours post dose (SMD 0.28, 95% CI 0.10 to 0.46; six studies), consistent with a small effect size according to Cohen's rules.
Fever in adults: Three studies concluded that ibuprofen was superior to acetaminophen and two studies reported no significant difference between treatments (five studies). No meta-analysis was performed.
Fever in children: Fifteen studies concluded that ibuprofen was superior to acetaminophen and 15 studies reported no significant difference between treatments. In the meta-analysis of RCTs, ibuprofen was associated with significantly lower fever scores at four hours post dose (SMD 0.26, 95% CI 0.10 to 0.41; seven studies), consistent with a small effect size using Cohen's rules.
Adverse events in adults: No studies found evidence of a significant difference between ibuprofen and acetaminophen in the incidence of one or more adverse events (35 studies). In the meta-analysis of RCTs, ibuprofen was associated with a lower (but not statistically different) incidence of adverse events than acetaminophen (OR 1.12, 95% CI 1.00 to 1.25; 25 studies), consistent with a small effect size using Cohen. One study found no difference in the rate of serious adverse events between treatments.
Adverse events in children: Twenty-nine studies found no evidence of a significant difference between ibuprofen and acetaminophen in the incidence of one or more adverse events. One study concluded that acetaminophen was safer or better tolerated than ibuprofen. In the meta-analysis, there was no evidence of a difference in the rates of adverse events between ibuprofen and acetaminophen (OR 0.82, 95% CI 0.60 to 1.12; 19 studies). Two studies found no evidence of a difference in the rate of serious adverse events between treatments.