Title: Dipyrone
CAS Registry Number: 5907-38-0
CAS Name: [(2,3-Dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)methylamino]methanesulfonic acid sodium salt monohydrate
Additional Names: (antipyrinylmethylamino)methanesulfonic acid sodium salt; 1-phenyl-2,3-dimethyl-5-pyrazolone-4-methylaminomethanesulfonate sodium; noraminopyrine methanesulfonate sodium; 4-methylamino-1,5-dimethyl-2-phenyl-3-pyrazolone sodium methanesulfonate; sodium methylaminoantipyrine methanesulfonate; methylmelubrin; methampyrone; metamizol; analgin; sulpyrin
Trademarks: Alginodia (Beta); Algocalmin; Bonpyrin (Takeda); Conmel (Winthrop); Divarine (Tutag); Dolazon (Graeub); D-Pron (Minnesota Pharm.); Dya-Tron (Myers-Carter); Espyre (SS Pharm.); Farmolisina (Centralvet); Feverall; Fevonil (Century); Keypyrone (Key); Metilon (Daiichi); Minalgin (Streuli); Narone (Ulmer); Nartate; Nevralgina (Climax); Nolotil (Boehringer, Ing.); Novacid; Novaldin (Winthrop); Novalgin (HMR); Novemina (Lazar); Novil; Paralgin; Pyralgin (Savage); Pyril (Maurry Biol.); Pyrilgin (Savage); Pyrojec (Maurry Biol.); Tega-Pyrone (Ortega); Unagen
Molecular Formula: C13H16N3NaO4S.H2O
Molecular Weight: 351.35
Percent Composition: C 44.44%, H 5.16%, N 11.96%, Na 6.54%, O 22.77%, S 9.13%
Literature References: Prepd by methylating the amino group of sulfamipyrine, then treating with formaldehyde sodium bisulfite soln: DE 254711; DE 259503; DE 259577 (all 1911 to Hoechst).
Properties: Minute crystals from alc. Sol in water (1 g/1.5 ml), methanol. Less sol in ethanol. Practically insol in ether, acetone, benzene, chloroform. Aq solns are neutral; may acquire a yellow discoloration without apparent potency loss.
Derivative Type: Magnesium salt
CAS Registry Number: 6150-97-6
Trademarks: Magnopyrol (Abbott)
Molecular Formula: C26H32MgN6O8S2
Molecular Weight: 645.00
Percent Composition: C 48.42%, H 5.00%, Mg 3.77%, N 13.03%, O 19.84%, S 9.94%
Therap-Cat: Analgesic; antipyretic.
Therap-Cat-Vet: Analgesic; antispasmodic.
Keywords: Analgesic (Non-Narcotic); Antipyretic.
Diresorcinol Dirithromycin Discodermolide Disilane Disodium Dihydrogen Hypophosphate

Metamizole sodium
Metamizole ball-and-stick.png
Systematic (IUPAC) name
sodium [(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)methylamino] methanesulfonate
Clinical data
AHFS/Drugs.com International Drug Names
Legal status Varies by country (see article)
Routes Oral, parenteral
Pharmacokinetic data
Half-life 1–4 hours
Excretion Renal
CAS number 68-89-3 YesY (sodium salt)
ATC code N02BB02
PubChem CID 80254
DrugBank DB04817
ChemSpider 6000 YesY
ChEBI CHEBI:59033 YesY
Chemical data
Formula C13H16N3NaO4S 
Mol. mass 333.337 g/mol
 YesY (what is this?)  (verify)

Metamizole (INN), or dipyrone, is a potent analgesic (pain reliever) and antipyretic (fever reducer), with results about two to four times more effective than those of ibuprofen and paracetamol. Metamizole sodium is marketed under various trade names, including Algozone, Algocalmin, Algopyrin, Analgin, Dipirona, Novalgin, Neo-Melubrina and Optalgin. Metamizole was first synthesized by the German company Hoechst AG (now part of Sanofi) in 1920, and its mass production started in 1922. It remained available worldwide until the 1970s, when it was linked with a small risk of causing agranulocytosis, a potentially fatal condition. Those results have been disputed in meta-analyses conducted in the 2000s.[1][2] Regardless, several national medical authorities have withdrawn metamizole from the market altogether or have restricted it to be available only with a prescription, although it remains available over the counter in many countries.[3]

Simultaneous consumption of metamizole and alcohol leads to almost instant and prolonged fatigue.

In 1998, Andrade et al. conducted a meta-analysis to compare epidemiologic studies from 1975 to 1995 and estimated that the excess mortality per million from community acquired cases of agranulocytosis, aplastic anaemia, anaphylaxis and serious upper gastrointestinal complications was 592 for diclofenac, 185 for aspirin, 25 for metamizole, and 20 for paracetamol.[1] CIOMS IV in the same year reported the excess mortality risk for the same conditions to be: diclofenac = 5.92; aspirin = 2.03; metamizole = 0.20; and paracetamol=0.25. These studies certainly suggest that the risks from adverse reactions to metamizole are similar to those posed by paracetamol, a drug widely reputed to be fairly safe. According to the CIOMS IV conclusion “Newer methods of epidemiological studies have shown that the risk of agranulocytosis (1.7 per million) due to metamizole was exaggerated in the 70’s”.[2]

A study in Sweden published in 2002 estimated the total risk during metamizole therapy for patients in hospitals (inpatients) and outside of hospital (outpatients) about 3 to 100 times greater than that estimated by Dr. Wong: "Given certain assumptions including the actual amounts prescribed the calculated risks of agranulocytosis would be approximately one out of every 31,000 metamizole-treated inpatients and one of every 1400 metamizole-treated outpatients."[4]

When considering the data available on the risks and benefits of metamizole, it is noteworthy that this generic non-steroidal anti-inflammatory drug is very inexpensive when compared to newer COX-2 selective preparations. This has the potential to reduce profits for pharmaceutical companies, theoretically producing financial motivation for its discontinuation.[5]