Variation in risk of adverse outcomes with metamizole

(HealthDay)—The magnitude of the risk of adverse outcomes associated with metamizole use varies in different studies, according to a review published online July 15 in the Journal of Clinical Pharmacy and Therapeutics.

Susan E. Andrade, Sc.D., from the University of Massachusetts Medical School in Worchester, and colleagues conducted a systematic review of the safety of metamizole. Data were included for 22 epidemiologic studies that met inclusion criteria.

The researchers found that most of the studies that examined agranulocytosis indicated an increased risk in association with metamizole use, with relative risk estimates varying from 1.5 to 40.2. Three case-control studies indicated no correlation between metamizole and aplastic anemia. Four of the five case-control studies that examined the risk of upper gastrointestinal bleeding showed a significantly increased risk associated with metamizole (relative risk estimates varied from 1.4 to 2.7). There was insufficient evidence to examine the risks of metamizole on other outcomes (such as hepatic effects, anaphylaxis, and congenital anomalies). The effects of dose, route of administration, and duration of therapy were examined in few studies.

"Further research is needed to better quantify the potential risks associated with metamizole compared to other non-narcotic analgesics," the authors write.

Two authors disclosed employment by Boehringer Ingelheim, a manufacturer of metamizole, which funded the study.

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