Meta-analysis of single dose oral tramadol plus acetaminophen in acute postoperative pain.

Background and objective: Trials in acute postoperative pain are usually small. Pooling homogenous data from a number of trials in a meta-analysis enables a truer estimate of efficacy. The aims of the present meta-analysis were to assess the analgesic efficacy and adverse effects of single-dose oral tramadol plus acetaminophen (paracetamol) in acute postoperative pain, and to demonstrate the efficacy of the combination formulation compared with its components.

Methods: Individual data from > 1400 adult dental or gynaecologic/orthopaedic patients with moderate-to-severe pain were taken from seven randomised, double-blind, placebo controlled trials of tramadol (75 mg or 112.5 mg) plus acetaminophen (650 mg or 975 mg) with identical methods. The primary outcome measure was the number of patients needed to be treated (NNT) for one patient to obtain at least 50% pain relief. Information on adverse effects was also collected and the number needed to harm (NNH) was estimated.

Results: The tramadol/acetaminophen combination was more effective than either of its two components administered alone. For dental patients, who formed the bulk of the population, the combination formulation also had a significantly lower (better) NNT (approximately 3) than the components al one (approximately 8-12), comparable to ibuprofen 400 mg. The adverse effects associated with tramadol/acetaminophen were similar to those associated with the components alone. The commonest were dizziness, drowsiness, nausea, vomiting and headache.

Conclusions: Meta-analysis confirmed the analgesic superiority of the combination treatment over its components, without additional toxicity. Combination analgesic formulations are an important and effective means of pain relief, and should prove useful in treating elderly and other groups of patients who often cannot tolerate non-steroidal anti-inflammatory drugs, including the newer COX-2 inhibitors.