Adverse drug events related to extemporaneous compounding medicines

Summary In the present study, we investigated the causality between adverse drug events and extemporaneous compounding from spontaneous reports generated by a healthy team in a medium-complexity public hospital in São Paulo state, Brazil. An observational cross-sectional study was conducted between August/2017 to July/2018. All adverse drug events spontaneous reports, which mentioned extemporaneous compounding, were evaluated. The selected variables were patient's clinical history, pharmacotherapy, adverse drug reactions, medication error and type of extemporaneous compounding. Causality assessment between the adverse drug reaction and extemporaneous compounding was performed by World Health Organization – Uppsala Monitoring Center algorithm and medication error analysis was performed by the National Council for Coordination of Reporting and Prevention of Medication Errors algorithm. 3,211 spontaneous reports were evaluated. Only 144 (4.5%) reports mentioned extemporaneous compounding, being 110 eligible for analysis. The causality assessment showed that in 27 (24%) reports the adverse drug reaction and medication error identified were possibly related to extemporaneous compounding, with an underreporting index of 0.87. From these 27 reports, 3 adverse drug reactions were classified as “probable” and 23 as “possible” whereas 4 medication error were classified as “error, harm: category E”. Although extemporaneous compounding is a common practice in hospitals, only a small portion of the reports included it. Future studies may investigate the use of extemporaneous compounding as a trigger tool for adverse drug reactions since this study shows that one out of four reports that mentioned it leads to patient harm.