Comparative safety profile of Metamizole, Viminol, and Tapentadol: a prospective observational study on adverse reactions

The most potent analgesics cause serious Adverse Drug Reactions (ADRs), so medications such as metamizole, viminol, and tapentadol may be alternatives. However, the safety of these analgesics still needs to be better understood. This study aims to assess prospective ADRs associated with these analgesics in a pain clinic. We followed up with the patients who had used these medicines for 45 days, classified the ADRs according to severity (mild, moderate or severe), mechanism (type A or type B), and incidence (very common, common, uncommon, and rare), and determined the causality. Among 240 patients, three ADRs to metamizole, seven to viminol, and 11 to tapentadol alone were documented. Additionally, 22 suspected ADRs were attributed to potential drug interactions among these analgesics and other medications. The ADRs were categorized as mild to moderate, type A, and common or uncommon. Causality was categorized as certain or possible. The ADRs induced by viminol were associated with age, with each year of age leading to a 6% increase in risk of ADRs, according to a logistic regression model applied specifically to this drug. No other association was found between tapentadol or viminol and comorbidities. It was not possible to analyze the metamizole data due to its low incidence. Overall, metamizole was the safest, reinforcing its safety profile and its valuable indication in the treatment of pain.