Aminopyrine

BackgroundMetamizole is used to treat pain in many parts of the world. Information on the safety profile of metamizole is scarce; no conclusive summary of the literature exists.ObjectiveTo determine whether metamizole is clinically safe compared to placebo and other analgesics.MethodsWe searched CENTRAL, MEDLINE, EMBASE, CINAHL, and several clinical trial registries. We screened the reference lists of included trials and previous systematic reviews. We included randomized controlled trials that compared the effects of metamizole, administered to adults in any form and for any indication, to other analgesics or to placebo. Two authors extracted data regarding trial design and size, indications for pain medication, patient characteristics, treatment regimens, and methodological characteristics. Adverse events (AEs), serious adverse events (SAEs), and dropouts were assessed. We conducted separate meta-analyses for each metamizole comparator, using standard inverse-variance random effects meta-analysis to pool the estimates across trials, reported as risk ratios (RRs). We calculated the DerSimonian and Laird variance estimate T2 to measure heterogeneity between trials. The pre-specified primary end point was any AE during the trial period.ResultsOf the 696 potentially eligible trials, 79 trials including almost 4000 patients with short-term metamizole use of less than two weeks met our inclusion criteria. Fewer AEs were reported for metamizole compared to opioids, RR = 0.79 (confidence interval 0.79 to 0.96). We found no differences between metamizole and placebo, paracetamol and NSAIDs. Only a few SAEs were reported, with no difference between metamizole and other analgesics. No agranulocytosis or deaths were reported. Our results were limited by the mediocre overall quality of the reports.ConclusionFor short-term use in the hospital setting, metamizole seems to be a safe choice when compared to other widely used analgesics. High-quality, adequately sized trials assessing the intermediate- and long-term safety of metamizole are needed.

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most common cause of hypersensitivity reactions, with pyrazolones the most frequent drugs inducing selective reactions. Immediate selective hypersensitivity to pyrazolones is thought to be mediated by specific-IgE. Sensitivity of in vitro diagnostic tests is low and this may be due to the incomplete characterization of the structures involved. Here we investigated whether main metabolites of metamizole (dipyrone) in human could be involved in the immune response using the basophil activation test (BAT). We studied subjects with confirmed selective immediate hypersensitivity to metamizole and performed BAT with metamizole and its metabolites: 4-methylamino-antipyrine (MAA), 4-aminoantipyrine (AA), 4-acetylamino-antipyrine (AAA) and 4-formylamino-antipyrine (FAA). BAT results showed an increase of positive results from 37.5% to 62.5% using metamizole plus metabolites as compared with the BAT carried out only with the parent drug, demonstrating that metamizole metabolites have a role in the reaction and can induce specific basophil activation in patients with immediate hypersensitivity to this drug. Our findings indicate that pyrazolone metabolites are useful for improving the in vitro diagnosis of allergic reactions to metamizole.

Three compounds derived from 4-aminoantipyrine (AA) were synthesized and their structures confirmed by melting point, elemental analysis, FT-IR, and 1H-NMR. The molecular structures of the four compounds were characterized by single-crystal X-ray diffraction and calculated by using the density functional theory (DFT) method with 6-31G (d) basis set. The calculated molecular geometries and the vibration frequencies of the AA derivatives in the ground state have been compared with the experimental data. The results show that the optimized geometries can reproduce well the crystal structural parameters, and the theoretical vibration frequencies show good agreement with the experimental data, although the experimental data are different from the theoretical ones due to the intermolecular forces. Besides, the molecular electrostatic potential (MEP) and the frontier molecular orbital (FMO) analysis of the compounds were investigated by theoretical calculations.

This study aims to analyze self-reported dipyrone use among the Brazilian population. We used data from the Brazilian National Survey on Access, Use, and Promotion of Rational Use of Medicines (PNAUM), conducted from September 2013 to February 2014 in urban areas of five regions of Brazil. The study population included individuals of all ages, with a minimum sample size of 960 interviews per sample domain, totaling 41,433 respondents and representing approximately 17 million Brazilians. We assessed socioeconomic and demographic characteristics, profiles of chronic and acute diseases, medication use, health perceptions, and perceived effectiveness and safety of dipyrone - either alone or in combination with other medications. The Poisson regression model was used to estimate adjusted prevalence ratios (aPR). The results showed that 10.4% of respondents reported using dipyrone, with 98.3% of these users taking it for acute conditions, such as pain (77.9%) and fever (14.5%). After adjusting for variables, dipyrone use for pain was more common among women (aPR = 1.66; 95%CI: 1.47-1.88) and among individuals living in the Central-West (aPR = 1.32; 95%CI: 1.04-1.67), particularly those with chronic conditions or acute events. Use for fever was similar between genders but more common among children aged under 10 years (PR = 0.62; 95%CI: 0.46-0.82). Half of the users combined dipyrone with other medications, and this practice was ten times more frequent for pain than for fever. Lastly, the effectiveness of dipyrone was widely perceived as positive, with few reports of adverse effects.