Metamizole, or dipyrone, is a painkiller, spasm reliever, and fever reliever that also has anti-inflammatory effects. It is most commonly given by mouth or by intravenous infusion.

Although it is available over-the-counter in some countries, it is banned in others, due to its potential for adverse events, including agranulocytosis.

A study by one of the manufacturers of the drug found the risk of agranulocytosis within the first week of treatment to be a mere 1.1 in a million, versus 5.92 in a million for diclofenac.[8] It is in the ampyrone sulfonate family of medicines.

It was patented in 1922 and was first used medically in Germany under the brandname “Novalgin”. For many years, it was available over-the-counter in most countries, before its withdrawal due to severe adverse effects.

Metamizole is marketed under various trade names.