Possibilities of Using Metamizole in the Treatment of Acute Primary Headaches
The aim of the review article by Brazilian authors was to summarize the efficacy and safety of metamizole in the treatment of acute primary headaches, such as migraine, episodic tension-type headache (ETTH), cluster headache, and unclassified primary pain in adults and children.
Introduction
Headache predominantly affects people of working age and is often reported by both outpatient and hospitalized patients. Most headaches are benign but they impair quality of life and reduce productivity.
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Metamizole (dipyrone) is a pyrazolone derivative that is a popular non-opioid analgesic in many countries. Its efficacy is considered comparable to some opioid analgesics. It is used to treat various types of pain including headaches and can be administered orally or intravenously. The risk of agranulocytosis, which can rarely occur as an adverse event, has not yet been sufficiently quantified.
Evaluated Studies
The authors searched for double-blind randomized controlled trials that evaluated the efficacy of metamizole in the symptomatic relief of acute primary headaches. Four studies met the criteria, involving a total of 636 adult participants and using the diagnostic criteria of the International Headache Society (IHS). Two studies evaluated metamizole for ETTH, one in oral form and the other in intravenous form, and two studies evaluated metamizole for migraine, with one not reporting pain-related outcomes. No studies were found in the pediatric population.
Results
Oral Metamizole in the Treatment of ETTH
A study with 356 participants evaluated the effects of oral metamizole in patients with at least 2 episodes of moderate ETTH. Metamizole at doses of 0.5 g or 1 g, acetylsalicylic acid (ASA) at a dose of 1 g, and placebo were compared. The analgesic effect of metamizole was significantly greater than placebo at both doses, and the 1 g dose showed greater efficacy than ASA.
Intravenous Metamizole in the Treatment of ETTH
A smaller placebo-controlled study (n = 60) evaluated intravenous metamizole at a dose of 1 g. Metamizole showed significant efficacy in terms of complete suppression or relief of pain.
Intravenous Metamizole in the Treatment of Migraine
The effects of metamizole on pain relief in patients with migraines were evaluated in a placebo-controlled study. This included 134 patients and metamizole was administered intravenously at a dose of 1 g. Significant pain relief or complete suppression was observed in the active treatment group.
Safety
No serious adverse events were reported, and no significant differences were found in the incidence of adverse events between metamizole and comparators (placebo or ASA).
Conclusion
The studies included in this review confirm the efficacy of metamizole in pain relief for adult patients with ETTH and migraine. However, the relatively small number of participants evaluated for safety prevents a proper assessment of potential risks. According to the State Institute for Drug Control (SÚKL) in the Czech Republic, no cases of metamizole-induced agranulocytosis have been reported to date. Nevertheless, it is recommended to inform both doctors and patients about this risk.
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Sources:
1. Ramacciotti A. S., Soares B. G., Atallah A. N. Dipyrone for acute primary headaches. Cochrane Database Syst Rev 2014; 7: CD004842, doi: 10.1002/14651858.CD004842.pub3.
2. SÚKL. Metamizole and blood disorders. Available at: www.sukl.eu/file/660_1_2
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