The antipyretic effectiveness of dipyrone in the intensive care unit: A retrospective cohort study

Introduction: Dipyrone (metamizol) is regularly used in critical care for pain and fever treatment, especially in Germany and Spain. However, indication for antipyretic therapy in critically ill patients is currently unclear and data for both the risk and benefit of dipyrone treatment in the intensive care environment are scarce. We hypothesized that antipyretic efficiency of dipyrone would not exceed antipyretic efficiency of acetaminophen. We therefore aimed to compare temperature courses in critically ill patients receiving either intravenous dipyrone, acetaminophen or no antipyretic medication.

Material and methods: We included 937 intensive care unit (ICU) patients with body temperature recordings of at least 37.5°C. We investigated temperature decrease associated with dipyrone or acetaminophen and additionally compared it to an untreated control group.

Results: Within the eight-hour study interval, maximum body temperature decrease in patients without antipyretic medication was -0.6°C (IQR: -1.0 to -0.4°C; n = 315). Maximal decrease in body temperature was higher both with dipyrone (-0.8°C (IQR: -1.2 to -0.4°C); p = 0.016; n = 341) and acetaminophen (-0.9°C (IQR: -1.6 to -0.6°C); p<0.001; n = 71), but did not differ between dipyrone and acetaminophen (p = 0.066). As compared to untreated patients, dipyrone only led to a marginal additional decrease in body temperature of only -0.1°C. Maximum of antipyretic effectiveness was reached four hours after administration.

Conclusion: Antipyretic effectiveness of dipyrone in ICU patients may be overestimated. Given the lack of prospective data, clinical evidence for antipyretic dipyrone therapy in the ICU is insufficient and warrants further critical evaluation.