Metamizole

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Not to be confused with methimazole .

Metamizole
Systematic (IUPAC) name
?
Identifiers
CAS number	68-89-3
ATC code	N02BB02
PubChem	80254
Chemical data
Formula	C13H17N3O4S
Mol. weight	311.358
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	?
Excretion	?
Therapeutic considerations
Pregnancy cat.	?
Legal status
Routes	?

Metamizole sodium ([(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl) methylamino] methanesulfonate) is a non-steroidal anti-inflammatory drug (NSAID), commonly used in the past as a powerful painkiller and fever reducer. It is better known under the names Dipyrone, Analgin, and Novalgin.

Metamizole was first synthesized by the German company Hoechst AG in 1920, and its mass production started in 1922. It remained freely available worldwide until the 1970s, when it was discovered that the drug carries a small risk of causing agranulocytosis - a very dangerous and potentially fatal condition. Recent studies estimate that the incidence rate of metamizole-induced agranulocytosis is between 0.2 and 2 cases per million person days of use, with approximately 7% of all cases fatal (provided that all patients have access to urgent medical care). In other words, one should expect 50 to 500 deaths annually due to metamizole in a country of 300 million, assuming that every citizen takes the drug once a month. This is not a very high rate, especially compared to other drugs - for example, the prescription drug clozapine is known to be at least 50 times more likely to trigger agranulocytosis. However, at the time the risk was assumed to be much greater [1] and, as such, excessive for an over-the-counter analgesic, especially considering the existence of safer alternatives (aspirin, paracetamol, and ibuprofen).

Metamizole was banned in Sweden in 1974, in the United States in 1977; more than 30 countries, including Japan, Australia, and most of the European Union, have followed suit. In these countries, metamizole is still occasionally used as a veterinary drug. Some pharmaceutical companies, notably Hoechst and Merck, continue to develop metamizole-containing drugs and market them in some countries. In Germany it became a prescription drug, sold under the brands Novalgin, Analgin, Berlosin, Metalgin, Metamizol-Puren, Novaminsulfon.

In the rest of the world (esp. in Mexico, India, Brazil, Russia, Third World countries) metamizole is still freely available over-the-counter and remains one of the most popular analgesics. For example, metamizole and metamizole-containing drugs account for 80% of OTC analgesic market in Russia, whereas ibuprofen accounts for 2.5%. In Romania it is sold under the brands Algocalmin, Novocalmin, Algozone, Nevralgin, playing an important role in self-medication.

Metamizole received brief period of attention by American media in 2001[2], when a Latino immigrant boy was admitted into a Salt Lake City clinic with symptoms of agranulocytosis. It was discovered that the drug remained freely available in Latino shops and highly popular among Mexican immigrants, despite the ban.

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Analgesics (N02A, N02B) edit
Opioids:	Buprenorphine, Butorphanol, Codeine, Dextropropoxyphene, Dihydrocodeine, Fentanyl, Diamorphine (Heroin), Hydrocodone, Hydromorphone, Ketobemidone, Morphine, Nalbuphine, Oxycodone, Oxymorphone, Pentazocine, Pethidine (Meperidine), Tramadol
Salicylic acid and derivatives: Aspirin (Acetylsalicylic Acid), Diflunisal, Ethenzamide -- See also: NSAIDs
Pyrazolones:	Aminophenazone, Metamizole, Phenazone
Anilides:	Paracetamol (acetaminophen), Phenacetin
Others:	Ziconotide, Tetrahydrocannabinol