Metamizole sodium is a non-steroidal anti-inflammatory drug (NSAID), commonly used in many countries as a powerful painkiller and fever reducer. It is better known under the names Dipyrone, Analgin, Novalgin, and Melubrin.
Metamizole was first synthesized by the German company Hoechst AG (now part of Sanofi-Aventis) 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. Controversy remains regarding the level of risk. Several national medical authorities have banned metamizole either totally or have restricted it to be available only on prescription.
According to comments by Dr Anthony Wong of the University of São Paulo, Brazil in a WHO newsletter,[1] 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 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 and, as such, excessive for an over-the-counter analgesic, especially considering the existence of safer alternatives.
Metamizole was banned in Sweden in 1974, in the United States in 1977; more than 30 countries, including Japan, Australia, Iran, and part of the European Union, have followed suit. In these countries metamizole is still occasionally used as a veterinary drug. In Germany it became a prescription drug. Some European pharmaceutical companies, notably Hoechst and Merck, continue to develop metamizole-containing drugs and market them in some countries. In Sweden, the ban was lifted in 1995 and re-introduced in 1999 only to be taken off the market again just a few years later.
Propyphenazone or Isopropylantipyrine (C14H18N2O, 1,2-dihydro-1,5-dimethyl-4-(isopropyl)-2-phenyl-pyrazol-3-one) is a derivative of phenazone with similar analgesic and antipyretic effects.
Propyphenazone or Isopropylantipyrine (C14H18N2O, 1,2-dihydro-1,5-dimethyl-4-(isopropyl)-2-phenyl-pyrazol-3-one) is a derivative of phenazone with similar analgesic and antipyretic effects.
Phenazone, or phenazon, is an analgesic. It was first synthesised by Ludwig Knorr in 1883. It is formed by reducing diortho-dinitrodiphenyl with sodium amalgam and methyl alcohol, or by heating diphenylene-ortho-dihydrazine with hydrochloric acid to 150 C. It crystallizes in needles which melt at 156 C. Potassium permanganate oxidizes it to pyridazine tetracarboxylic acid.
Antipyretics are drugs that reduce body temperature in situations such as fever. However, they will not affect the normal body temperature if one does not have fever.
Antipyretics cause the hypothalamus to override an interleukin-induced increase in temperature. The body will then work to lower the temperature and the result is a reduction in fever.
Propyphenazone or Isopropylantipyrine (C14H18N2O, 1,2-dihydro-1,5-dimethyl-4-(isopropyl)-2-phenyl-pyrazol-3-one) is a derivative of phenazone with similar analgesic and antipyretic effects.
Dichloralphenazone is a 1:2 mixture of antipyrine with chloral hydrate. In combination with paracetamol and isometheptene, it is the active ingredient of medications for migraine and vascular (tension) headaches, including Epidrin and Midrin. Performance impairments are common with this drug and caution is advised, for example when driving motor vehicles. This drug acts on the blood vessels in the brain and causes them to constrict, thus relieving the pain of a headache or migrain. Additional uses of Dichloralphenazone include sedation for the treatment of short-term insomnia, although there are probably better drug choices for the treatment of insomnia.
