Treatment of postoperative pain after total hip arthroplasty: comparison between metamizol and paracetamol as adjunctive to opioid analgesics-prospective, double-blind, randomised study.

Introduction: Metamizole use has been limited because of its risk of agranulocytosis. However, more recent literature seems to support its safety. This prospective, randomised, double-blind study was conducted to compare the analgesic effects of intravenous metamizole or intravenous paracetamol in combination with morphine PCA during the first 24 h following total hip arthroplasty.

Materials And Methods: One hundred ten consecutive patients were selected for study. The two study groups were (A) metamizole, (B) paracetamol. Postoperative pain therapy was provided by Morphine PCA pump. In the first treatment group (A group), all patients received intravenous metamizole 1.5 g every 8 h during the first 24 postoperative hours. In the second treatment group (B group), all patients received intravenous paracetamol 1 g every 8 h during the first 24 postoperative hours. Postoperative pain intensity was measured 1, 2, 3, 4, 6, 8, 10, 14, 18, 22 h after the end of surgery by a VAS.

Results: Statistically significant differences in VAS pain values favoring metamizole were reported at 6-h (p = 0.038), 8-h (p = 0.036), 14-h (p = 0.011), 18-h (p < 0.001) and 22-h (p = 0.025) post-baseline. Mean cumulative pain values were 17.9 for metamizole and 30.6 for paracetamol.

Conclusions: In this study, we have also shown excellent efficacy of paracetamol and metamizole combined with opioids, but metamizole proved to be a better analgesic than paracetamol. It is also necessary to mention the financial aspect considering that intravenous paracetamol is about ten times more expensive than an equivalent analgesic doses of intravenous metamizole.