Metamizole, also known as metamizole sodium, is a non-steroidal anti-inflammatory drug (NSAID) similar to aspirin and ibuprofen that works as an analgesic, meaning it provides pain relief, and as an antipyretic, meaning it reduces fever. This drug was originally available without a prescription in most countries, but has been banned in more than 30 countries since the 1970s when its use was linked to a rare but sometimes fatal condition called agranulocytosis. The actual danger of taking metamizole is a matter of scientific debate, and in many countries the drug is still available over the counter and is used as part of pain and fever management in hospitals. In other countries, it is available, but only with a prescription. It is sold under many different brand names, including Dipyrone, Analgin, and Novalgin.
Until the 1970s, when the link to agranulocytosis was made, metamizole was generally considered a safe and effective NSAID that was especially potent when it came to reducing fever. It is still available over the counter in, for example, Spain, India, Mexico, Israel, and Russia, as well as many developing countries. In these countries it is often a popular drug that is considered both inexpensive and effective. Metamizole is currently banned in the United States, Canada, Sweden, Japan, Australia, and several other countries.
Agranulocytosis is a very serious condition characterized by a low white blood cell count and a suppressed immune system. Those suffering from this condition are very susceptible to infections like pneumonia and septicemia, also known as blood poisoning. Common symptoms include fever and sore throat, but are not present in all cases. This potentially fatal condition is a possible side effect not only of metamizole, but also of several other drugs, including other NSAIDs, such as naproxen, and the commonly prescribed anti-psychotic drug clozapine.
Many scientific studies have been done on the connection between metamizole and agranulocytosis, but they do not all agree on the risk of contracting the condition when taking the drug. Proponents of this drug believe that the risks were overestimated in the 1970s. Some recent studies have concluded that the risk is comparable to, or even lower than, the risk related to other medications. However, other studies have concluded that the risk of harmful side effects, including not only agranulocytosis, but also anaphylaxis and infant leukemia, is too great to allow the medication to be used. Those opposed to the use of metamizole believe it is preferable to use other drugs not associated with these risks.