Legitimate to extrapolate efficacy from one pain context to another: Is the third molar pain model different from other models and does it effect analgesic response?

Data sources Sources of literature were Medline, Embase, the Cochrane Library, Biological Abstracts and the Oxford Pain Relief Database. Study selection Randomised, double-blind trials were chosen that compared aspirin, ibuprofen or paracetamol with placebo in adult patients who had initially moderate or severe postoperative pain, and which measured pain intensity and relief using standard measurement tools over 4–6 h.Data extraction and synthesis Criteria for inclusion were: full peer-reviewed journal publication; randomised controlled trials that included single-dose treatment groups of aspirin, ibuprofen or paracetamol and placebo; double-blind design; baseline pain of moderate to severe intensity; patients over 15 years of age; at least 10 patients per group; and the pain outcome measures of total pain relief (TOTPAR) or summed pain intensity difference (SPID) over 4–6 h, or sufficient data to allow their calculation. Pain measures permitted for the calculation of TOTPAR or SPID were a standard five-point pain relief scale (none, slight, moderate, good, complete), a standard four-point pain intensity scale (none, mild, moderate, severe) or a standard visual analogue scale (VAS) for pain relief or pain intensity. Also accepted were the top two categories of a standard five-point global outcome scale (poor, fair, good, very good, excellent). Results Results from 160 comparisons of an analgesic versus placebo were included. These comprised 68 trials of aspirin at doses of 600/650 mg; 49 trials of ibuprofen at a dose of 400 mg; 19 trials of paracetamol at 600/650 mg; and 24 trials of paracetamol at 1000 mg. Dental studies predominated, forming 102 of the 160 studies (64%). There were no consistent differences between dental and postsurgical pain in single-dose trials of aspirin, either of two doses of paracetamol, or ibuprofen, where sufficiently large data sets exist to test the hypothesis. Only three out of 16 comparisons produced a statistically significant difference. Conclusions A systematic difference in the estimate of analgesic efficacy between dental and postsurgical pain models remains unproven and, on balance, no major difference is likely.