Metamizole (INN), or dipyrone (BAN, USAN), is an ampyrone sulfonate analgesic (pain reliever), antispasmodic (spasm reliever) and antipyretic (fever reducer) similar to paracetamol in that it has minimal anti-inflammatory effects and which is most commonly given orally or parenterally (by injection) to prevent and treat pain related to surgery or for the treatment of acute pain. It was first introduced into clinical use in Germany in 1922 under the brandname “Novalgin” and for many years it was available over-the-counter in most countries, until its toxicities became apparent, although in some countries it is available over-the-counter, its use is usually restricted in developed countries, due to its potential for causing toxic reactions.
|[(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)methylamino] methanesulfonic acid|
|Trade names||Originally Novalgin, now generic|
|AHFS/Drugs.com||International Drug Names|
|None assigned; no evidence of teratogenicity in animal studies, but use in the third trimester may cause adverse effects in the newborn or ductus arteriosus (a heart defect) due to its weak NSAID activity.|
|Legal status||Over-the-counter (some countries, see text); prescription-only (others); withdrawn (others)|
|Oral, IM, IV, rectal|
|Bioavailability||100% (active metabolites)|
|Protein binding||48%-58% (active metabolites)|
|Biological half-life||14 minutes (parent compound; parenteral); metabolites: 2–4 hours|
|Excretion||Urine (96%, IV; 85%, oral), faeces (4%, IV).|
|CAS Number||68-89-3 (sodium salt)|
|Molecular mass||311.357 g/mol|
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