Dose-response in direct comparisons of different doses of aspirin, ibuprofen and paracetamol (acetaminophen) in analgesic studies.
OBJECTIVE
Establishing the dose-response relationship for clinically useful doses of aspirin, ibuprofen and paracetamol has been difficult. Indirect comparison from meta-analysis is compromised by too little information at some doses.


METHODS
A systematic review of randomized, double-blind trials in acute pain comparing different doses of aspirin, ibuprofen and paracetamol was therefore undertaken.


RESULTS
Fifty trials were found. Numerical superiority of higher over lower dose was found by the original authors in 37/50 trials (74%) and statistical superiority in 11/50 (22%). Twenty-eight trials had design, quality and data reporting characteristics to allow pooling of common doses; in 3/28 (11%) of the individual trials our calculations showed statistical superiority of higher over lower dose. Pooled comparison of 1000/1200 mg aspirin over 500/600 mg was statistically superior, with a number-needed-to-treat (NNT) for higher over lower dose of 16 (8 to > 100). Pooled comparison of 400 mg ibuprofen over 200 mg was statistically superior, with an NNT for higher over lower dose of 10 (6-23). Pooled comparison of 1000 mg paracetamol over 500 mg was statistically superior, with an NNT for higher over lower dose of 9 (6-20).


CONCLUSIONS
Use of trials making direct comparison of two different doses of target drugs revealed the underlying dose-response curve for clinical analgesia.
McQuay
Henry J
HJ
Pain Research and Nuffield Department of Anaesthetics, (University of Oxford), Churchill Hospital, Oxford, UK. henry.mcquay@pru.ox.ac.uk
Moore
R Andrew
RA
D000082:Acetaminophen / Q000008:administration & dosage*; D000700:Analgesics / Q000008:administration & dosage*; D001241:Aspirin / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D007052:Ibuprofen / Q000008:administration & dosage*; D010147:Pain Measurement / Q000187:drug effects*; D016032:Randomized Controlled Trials as Topic
D000700:Analgesics; D000082:Acetaminophen; D001241:Aspirin; D007052:Ibuprofen