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Questions And Answer

• Overview

  Analgin[metamizole] is a painkiller, spasm reliever and fever reliever^[1]. However, it is now either prescription or banned in most developed countries due to its potential for adverse events, including agranulocytosis. It belongs to the ampyrone sulfonate family of medicines.
  Metamizole, a nonnarcotic analgesic, has been used to treat pain and fever for almost 90 years in some countries, while in others it is completely unknown or forgotten^{[2, 3]}. The German company Hoechst AG synthesized it in 1920, and its mass production started in 1922. Metamizole remained freely available worldwide until the 1970s, when it was found that the drug poses a risk of causing agranulocytosis^{[4, 5]}. Soon after that, metamizole was banned in the United States, Japan, Australia, and part of the European Union. However it is still widely used in some European countries, Turkey, Israel, India, Brazil, and Third World countries. Metamizole is available over-the-counter and remains one of the most popular analgesics in Bulgaria. Metamizole is a white or almost white crystalline powder, very soluble in water and soluble in alcohol. It is a well-established active substance and is the subject of a monograph in the European Pharmacopeia. Metamizole belongs to the following therapeutic groups: NSAIDs, nonnarcotic analgesics. ATC code is N02BB02^{[6, 7]}. ;

• Indication

  Metamizole has various effects including analgesic effect; antipyretic effect, anti-inflammatory effect and can reduce platelet aggregation. Metamizole is commonly used to treat postoperative pain, colic pain, cancer pain and migraine^{[8, 9]}. In many parts of the world, including most countries in the European Union and Latin America, it is the most popular non-opioid first-line analgesic and is sometimes even available over-the-counter. A few countries however, including the United States, the United Kingdom, Sweden, and most recently India^[4], have banned metamizole because health authorities judged the risk of agranulocytosis to outweigh the benefits^[5–7]. In addition, it can also be used in relieving fever, and treatment of respiratory and gastroenteritic diseases. It’s also helpful and efficacious in the treatment of blood poisoning and pyogenic dermatitis. Indications include asthma, pneumonia^[10]. ;

• Pharmacological effects and Mode of action

  The pharmacological mechanism of action of metamizole is not precisely known. Similar to paracetamol/acetaminophen, its effects may result from the interference with prostaglandin synthesis through the inhibitory potential on different cyclooxygenase[COX] isoenzymes. Yet, interactions with the endogenous opioid, peroxidase, cannabinoid, and glutamate systems are also discussed. The pharmacologically active metabolites of metamizole, MAA and AA, did not inhibit COX activity in vitro like classical COX inhibitors, but instead redirected the prostaglandin synthesis, ruling out inhibition of COX through binding to its active site^[11,12]. There is the assumption that metamizole might be an inhibitor of the COX-3 isoenzyme, thereby reducing prostaglandin synthesis in the dorsal horn of the spinal cord^{[11, 12, 14, 18]}.
  At least it may also have antinociceptive actions that are independent of the ability to inhibit COX. One component of the non-COXmediated antinociceptive effects is a consequence of direct actions on nociceptive afferent elements in the periphery. In addition to the action upon peripheral tissues, the NSAIDs exert their antinociceptive effect by acting upon the CNS, specifically upon the spinal cord and the periaqueductal grey matter[PAG], which triggers descending inhibition of spinal nociception^{[12, 13]}. Inhibition of prostaglandin synthesis also leaves more arachidonic acid available for the synthesis of endocannabinoids, which have an antinociceptive action in the spinal cord.
  Overall, It is still debated whether the site of metamizole action is in the CNS or in the periphery or both. The mode of action of metamizole has not been fully elucidated yet. Metamizole exerts its analgesic effects through several action mechanisms, among which the best described are COX inhibition^[11], delayed activation of the L-arginine/NO/cGMP/K+ channel pathway at the periphery and at the spinal cord^{[14, 15]}, activation of the descending inhibitory pain control system, interaction with the glutamatergic system^[16], and release of endogenous opioid peptides^[17]. ;

• Adverse reaction

  Although used for more than 90 years, the risks and harms of metamizole are not well documented, and information on adverse events related to metamizole is scarce. There are no large randomized controlled trials or conclusive summaries of the existing literature. Three current Cochrane reviews on the effectiveness and safety of metamizole for acute postoperative pain^[8], acute renal colic pain^[9], and acute primary headaches^[19] concluded that metamizole offers good short-term pain relief. In each of these systematic reviews, however, the number of included participants was too small and the authors did not conduct a meta-analysis of safety issues, but they did associate metamizole with somnolence, gastric discomfort and nausea. ;

• Warning and precaution

  In severe cases, metamizole can cause severe adverse reactions including congenital defect including aplasia cutis, craniofacial malformations[facial dysmorphism; choanal atresia], gastrointestinal malformations[esophageal atresia with or without tracheoesophageal fistula], omphalocele and abnormalities of the omphalomesenteric duct. Moreover, it may cause agranulocytosis, liver toxicity and hypothyroidism^[20]. ;

• References

  1. 1. Brayfield, A, ed.[13 December 2013]. "Dipyrone". Martindale: The Complete Drug Reference. Pharmaceutical Press. Retrieved 19 April 2014.
  2. https://www.un.org/esa/coordination/CL12.pdf
     Arellano, F, and J. A. Sacristán. "Metamizole: reassessment of its therapeutic role." European Journal of Clinical Pharmacology 38.6(1990]: 617-619.
  3. Oricha, B. S., and M. B. Yauri. "Dipyrone[Novalgin Metamizole]: banned and unbanned: the dilemma of a commonly prescribed and over the counter analgesic, [letter]." Annals of African Medicine 2.2(2004]: 101-102.[5-8]
  4. Bhaumik S. India’s health ministry bans pioglitazone, metamizole, and flupentixol-melitracen. BMJ. 2013; 347: f4366. doi: 10.1136/bmj.f4366 PMID: 23833116
  5. Andersohn F, Konzen C, Garbe E. Systematic review: agranulocytosis induced by nonchemotherapy drugs. Ann Intern Med. 2007; 146: 657–665. PMID: 17470834
  6. Andrade SE, Martinez C, Walker AM. Comparative safety evaluation of non-narcotic analgesics. J Clin Epidemiol 1998; 51: 1357–1365. PMID: 10086830
  7. Heimpel H. Drug-induced agranulocytosis. Med Toxicol Adverse Drug Exp. 1988; 3: 449–462. PMID: 3063921
  8. Derry S, Faura C, Edwards J, McQuay HJ, Moore RA. Single-dose dipyrone for acute postoperative pain. Cochrane Database Syst Rev. 2013;CD003227. doi: 10.1002/14651858.CD003227.pub3 PMID: 24277663
  9. Edwards J, Meseguer F, Faura C, Moore RA, McQuay HJ. Single dose dipyrone for acute renal colic pain. Cochrane Database Syst Rev. 2011;CD003867. doi: 10.1002/14651858.CD003867 PMID: 12519613
  10. https://www.lybrate.com/medicine/analgin
  11. Chandrasekharan NV, Dai H, Roos KLT, et al. COX-3, a cyclooxygenase-1 variant inhibited by acetaminophen and other analgesic/antipyretic drugs: cloning, structure, and expression. Proc Natl Acad Sci U S A 2002; 99: 13926–13931.
  12. Vanegas, H, and H. G. Schaible. "Prostaglandins and cyclooxygenases [correction of cycloxygenases] in the spinal cord. " Progress in Neurobiology 64.4(2001]:327.
  13. Vanegas, H, and V. Tortorici. "Opioidergic effects of nonopioid analgesics on the central nervous system. " Cellular & Molecular Neurobiology 22.5-6(2002]: 655-661.
  14. Campos, Carmen, et al. "Regulation of cyclooxygenase activity by metamizol." European Journal of Pharmacology 378.3(1999]: 339-347.
  15. Aguirrebañuelos, P, and V. Granadossoto. "Evidence for a peripheral mechanism of action for the potentiation of the antinociceptive effect of morphine by dipyrone. " Journal of Pharmacological & Toxicological Methods 42.2(1999]:79-85.
  16. Beirith, A, et al. "Spinal and supraspinal antinociceptive action of dipyrone in formalin, capsaicin and glutamate tests. Study of the mechanism of action. " European Journal of Pharmacology345.3(1998]:233-245.
  17. Hernández-Delgadillo, G. P., and S. L. Cruz. "Endogenous opioids are involved in morphine and dipyrone analgesic potentiation in the tail flick test in rats." European Journal of Pharmacology 546.1(2006]:54-59.
  18. Soltesz, S, et al. "Parecoxib versus dipyrone[metamizole] for postoperative pain relief after hysterectomy : a prospective, single-centre, randomized, double-blind trial." Clinical Drug Investigation28.7(2008]:421-428.
  19. Ramacciotti AS, Soares BGO, Atallah AN. Dipyrone for acute primary headaches. Cochrane Database Syst Rev. 2007;CD004842. doi: 10.1002/14651858.CD004842.pub3 PMID: 17443558
  20. https://www.rxlist.com/tapazole-drug.htm#warnings_precautions
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