Combination analgesic efficacy: individual patient data meta-analysis of single-dose oral tramadol plus acetaminophen in acute postoperative pain.

The primary aims of this study were to assess the analgesic efficacy and adverse effects of single-dose oral tramadol plus acetaminophen in acute postoperative pain and to use meta-analysis to demonstrate the efficacy of the combination drug compared with its components. Individual patient data from seven randomized, double blind, placebo controlled trials of tramadol plus acetaminophen were supplied for analysis by the R.W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey, USA. All trials used identical methods and assessed single-dose oral tramadol (75 mg or 112.5 mg) plus acetaminophen (650 mg or 975 mg) in adult patients with moderate or severe postoperative pain. Summed pain intensity and pain relief data over six and eight hours and global evaluations of treatment effect after eight hours were extracted. Number-needed-to-treat (NNT) for one patient to obtain at least 50% pain relief was calculated. NNTs derived from pain relief data were compared with those derived from pain intensity data and global evaluations. Information on adverse effects was collected. Combination analgesics (tramadol plus acetaminophen) had significantly lower (better) NNTs than the components alone, and comparable efficacy to ibuprofen 400 mg. This could be shown for dental but not postsurgical pain, because more patients were available for the former. Adverse effects were similar for the combination drugs and the opioid component alone. Common adverse effects were dizziness, drowsiness, nausea, vomiting, and headache. In sum, this meta-analysis demonstrated analgesic superiority of the combination drug over its components, without additional toxicity.