Metamizole

Metamizole is a sulfonic acid and comes in calcium, sodium and magnesium salt forms. Its sodium salt monohydrate form is a white/almost crystalline powder that is unstable in the presence of light, highly soluble in water and ethanol but practically insoluble in dichloromethane.

Metamizole has a potential of blood-related toxicity (blood dyscrasias), Like NSAIDs, it can trigger bronchospasm or anaphylaxis, especially in those with asthma.Serious side effects include agranulocytosis, aplastic anaemia, hypersensitivity reactions (like anaphylaxis and bronchospasm), toxic epidermal necrolysis and it may provoke acute attacks of porphyria.

Metamizole is banned in several countries, available by prescription in others (sometimes with strong warnings, sometimes without), and available over the counter in yet others.For example, approval was withdrawn in Sweden (1974), the US (1977),and India (2013, ban lifted in 2014).