Metamizole

Metamizole
Clinical data
Trade names	Novalgin, Algocalmin, Analgin, others
Other names	Dipyrone (BAN UK, USAN US), Sulpyrine (JAN JP)
AHFS/Drugs.com	International Drug Names
Pregnancy; category	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.;
Routes of; administration	Oral, IM, IV, rectal
ATC code	N02BB02 (WHO) ;
Legal status
Legal status	AU: Withdrawn; BR: OTC (Over the counter); CA: Veterinary only; DE: § 48 AMG/§ 1 MPAV (Prescription only); NZ: Prescription only; UK: Withdrawn; US: Veterinary only (horses); EU: Legally available;
Pharmacokinetic data
Bioavailability	100% (active metabolites)
Protein binding	48–58% (active metabolites)
Metabolism	Liver
Elimination half-life	14 minutes (parent compound; parenteral); metabolites: 2–4 h
Duration of action	4–6 h
Excretion	Urine (96%, IV; 85%, oral), faeces (4%, IV).
Identifiers
	IUPAC name [(2,3-Dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)methylamino] methanesulfonic acid;
CAS Number	50567-35-6 ; 68-89-3 (sodium salt);
PubChem CID	3111; 522325;
DrugBank	DB04817 ;
ChemSpider	3000 ;
UNII	934T64RMNJ;
KEGG	D08188 ;
ChEBI	CHEBI:62088 ;
ChEMBL	ChEMBL461522 ;
CompTox Dashboard (EPA)	DTXSID8020543 ;
ECHA InfoCard	100.000.631
Chemical and physical data
Formula	C13H17N3O4S
Molar mass	311.36 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES c1ccccc1N2N(C)C(C)=C(C2=O)N(C)CS(=O)(=O)O;
	InChI InChI=1S/C13H17N3O4S/c1-10-12(14(2)9-21(18,19)20)13(17)16(15(10)3)11-7-5-4-6-8-11/h4-8H,9H2,1-3H3,(H,18,19,20) ; Key:LVWZTYCIRDMTEY-UHFFFAOYSA-N ;
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Metamizole or dipyrone (informally known as the "Mexican aspirin") is a painkiller, spasm reliever, and fever reliever drug. It is most commonly given by mouth or by intravenous infusion. It belongs to the ampyrone sulfonate family of medicines and was patented in 1922. Metamizole is marketed under various trade names. It was first used medically in Germany under the brand name "Novalgin", later becoming widely known in Slavic nations and India under the name "Analgin".

Sale of Metamizole is restricted in some jurisdictions following studies in the 1970s which correlated it to severe adverse effects, including agranulocytosis. Other studies have disputed this judgement, instead claiming that it is a safer drug than other painkillers. Metamizole is popular in many countries, where it is typically available as an over-the-counter medication.