Metamizole vs. Tramadol in Postoperative Analgesia

Metamizole vs. Tramadol in Postoperative Pain Management

Study Methodology and Course

The Spanish multicenter randomized double-blind and controlled study included 151 women aged 18 to 60 years who underwent abdominal hysterectomy under general anesthesia.

The patients were divided into the metamizole group (n = 73) and the tramadol group (n = 78). Immediately after surgery, all patients received an intravenous loading dose of analgesic, followed by intravenous maintenance infusion and intravenous boluses of the evaluated drugs on demand, up to a maximum predetermined daily dose of 8 g of metamizole or 500 mg of tramadol. The study lasted 24 hours.

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Results

The average number of boluses in the metamizole group was 3.8 and in the tramadol group 3.5. The difference in the proportion of patients who needed rescue medication with morphine was not statistically significant (26.9% in the metamizole arm, 26.8% in the tramadol arm). Other parameters of analgesic efficacy, such as pain intensity, pain relief according to patient assessment, or the number of patients requiring the administration of the maximum established daily dose, did not differ between the groups.

The tramadol group showed a significantly higher incidence of gastrointestinal side effects than the metamizole group (42.1% vs. 20.2%; p < 0.05). Administration of the antiemetic ondansetron was necessary in a significantly higher number of patients treated with tramadol compared to metamizole (after 1 hour 19% vs. 7%; after 2 hours 26% vs. 11%; after 24 hours post-surgery 46% vs. 29%; p < 0.05).

Conclusion

Metamizole and tramadol showed similar efficacy in reducing acute pain after abdominal hysterectomy. Nausea and vomiting were more common in patients treated with tramadol.

Continuous Infusion vs. Patient-Controlled Analgesia

Study Methodology and Course

A 48-hour German study compared two methods of intravenous administration of a combination of tramadol and metamizole, either by continuous infusion or by a pump controlled by the patient (PCA – patient controlled analgesia). The study included 203 patients who had undergone abdominal surgery.

All participants received a combination of tramadol (20 mg/ml) and metamizole (200 mg/ml), either as a 1 ml bolus (for PCA) or in continuous infusion (rate 0–8 ml/h).

Pain scores, analgesic consumption, and the proportion of patients not responding to treatment were compared. Lack of response to treatment was defined as the need for rescue medication during the 48-hour study period or the patient's assessment of analgesia as inadequate in the final interview.

Results

Data were obtained from 191 patients, specifically 94 who received the drugs by infusion and 97 with PCA. More favorable results were observed in the PCA arm. The group using analgesics by infusion had higher tramadol consumption (1009.4 ± 494.4 mg/48 hours vs. 813.0 ± 585.3 mg/48 hours; p < 0.001) and a higher proportion of patients not responding to treatment (31.9% vs. 18.6%; p = 0.03). The average pain score did not differ between the groups. In the infusion arm, there was also a greater need for interventions by healthcare staff to adjust the infusion rate (min to max: 1–15 vs. 0–2).

Conclusion

The application of tramadol and metamizole using PCA proved to be an alternative option for postoperative pain management. The advantage of this regime is a more individualized approach, resulting in lower analgesic consumption, a higher proportion of responses to treatment, and fewer interventions by healthcare staff compared to continuous infusion.

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Sources:
1. Torres L. M., Rodríguez M. J., Montero A. et al. Efficacy and safety of dipyrone versus tramadol in the management of pain after hysterectomy: a randomized, double-blind, multicenter study. Reg Anesth Pain Med 2001; 26 (2): 118–124, doi: 10.1053/rapm.2001.21437.
2. Stamer U. M., Höthker F., Lehnen K., Stüber F. Postoperative analgesia with tramadol and metamizol. Continual infusion versus patient controlled analgesia. Anaesthesist 2003; 52: 33–41, doi: 10.1007/s00101-002-0427-1.