Metamizole

Metamizole - Use | Dose | Side Effects

Metamizole is a drug that belongs to the group of analgesics. It is used to treat severe post-traumatic or post-operative pain when treatment with other non-opioid medicines had no results. Metamizole is banned in many countries (including the USA) because it can cause agranulocytosis (severe reduction in the number of leukocytes in the blood) which may lead to the number of infections that can be life-threatening.

The mechanism of action is based on the inhibition of central cyclooxygenase-3 and on the activation of cannabinoid and opiodergic system.1

Precautions and contraindications

Although it is banned in most countries in the world, this drug is still used in many countries in Europe. That's because research has shown that this drug very rare causes agranulocytosis. One meta-analysis that included thousands of patients who were taking this drug, compared the incidence of side effects in patients taking Metamizole with an incidence of side effects in patients taking paracetamol and NSAID.2 This meta-analysis showed that patients taking Metamizole had no increased risk of serious side effects.

Another study conducted in Poland showed that this drug is completely safe if used for short period of time and in a hospital setting.3

However, if you notice symptoms of a cold or flu, immediately stop the treatment and contact your doctor.

Metamizole is contraindicated in the following conditions:

  • Deficiency of glucose-6-phosphate dehydrogenase
  • Severe hepatic insufficiency
  • Severe renal insufficiency
  • Acute intermittent porphyria
  • Pregnancy
  • Patients younger than 18 years

It must be used with extra precaution in patients who have low blood pressure, because Metamizole may cause hypotension.

Metamizole, pregnancy and breastfeeding

Metamizole is contraindicated in pregnant women and nursing mothers. It passes into breast milk and may harm your baby.

How to use

Recommended dose is 500 mg (one tablet) 3-4 times a day. The maximum daily dose is 4000 mg (8 tablets).

Overdose

There have been reports that one patient took 15 grams of Metamizole but he/she has not experienced any serious side effects. Overdose is generally rare, but when it occurs, it is manifested by the following symptoms:

  • Nausea
  • Vomiting
  • Seizures
  • Dizziness
  • Coma
  • Mydriasis
  • Liver damage
  • Kidney damage

Interactions

Metamizole may increase the effect of the following drugs which lead to increased risk of toxicity:

  • Anti-coagulants, such as:
    • warfarin
    • acenocoumarol
    • heparin and others
  • Antibiotics (penicillin and sulfonamides)
  • Corticosteroids
  • Drugs used to treat diabetes
  • Antiplatelet drugs (e.g. clopidogrel)
  • Anti-hypertensive drugs (e.g. diuretics and ACE inhibitors)

Drugs that can increase the levels of Metamizole in the blood and lead to adverse effects are:

  • Sedatives
  • Hypnotics

Metamizole can reduce the effects of cyclosporine.

It should not be administered concurrently with alcoholic beverages.

Adverse reactions

Metamizole can cause the following adverse reactions:

  • Abdominal discomfort
  • Maculopapular rash
  • Stevens-Johnson syndrome
  • Lyell syndrome
  • Agranulocytosis (sore throat, inflammation of the mouth, painful swallowing, fever and cough)
  • Hypotension
  • Bronchospasm
  • Arrhythmia
  • Allergic reactions

References

  1. NCBI link 1
  2. NCBI link 2
  3. NCBI link 3