To use or not to use dipyrone? Or maybe, Central Station versus ER? That is the question…

Dipyrone is a kind of pyrazolone derivative sold as an over-the-counter painkiller, which is very popular in Brazil.Its use has become so impregnated in our lives that, in a scene in the movie "Central Station", the character played by the Academy Award nominee Fernanda Montenegro was shown keeping a small bottle of dipyrone in a drawer with her keys and some money.This portrayal was not a chance occurrence.In a recent survey among outpatients of Hospital das Clinicas in São Paulo, Brazil, dipyrone was cited as the number one painkiller by more than 50% of the participants.1 Dipyrone is widely used, not only in Brazil but also in other countries such as France, Germany, Hungary, Israel, Spain, Sweden, and Thailand.However, the use of dipyrone was proscribed more than twenty years ago in the United States of America due to its putative role in depressing bone marrow and causing aplastic anemia and agranulocytosis in association with its use.What are the facts (evidence and hearsay) regarding dipyrone?Dipyrone was developed in Germany many years ago but, as a consequence of its proscription in the USA, few clinical trials have been performed to evaluate either its efficacy or safety as a painkiller in the era of evidence-based medicine.However, ancillary studies addressing the analgesic effect of dipyrone have been made using adequate methodology.Recently, a paper published by a Brazilian team has shown the positive effect of metamizol (intravenous sodium dipyrone) in acute migraine and tension-type headache treatment in a placebo-controlled clinical trial. 2 A cooperative trial published in Cephalalgia comparing metamizol and aspirin for treatment of episodic tensiontype headache has shown that more profound pain relief was provided by 0.5 and 1 g metamizol than did 1 g ASA. 3 Now we also have various studies from different countries and populations that have evaluated a possible association between dipyrone and blood dyscrasia, using good methodologies.A French study on drug use and aplastic anemia has demonstrated no correlation between this condition and previous use of dipyrone derivatives.4 The