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drugs

metamizole

Generality

Metamizole (or dipirone) is a non-steroidal anti-inflammatory drug (NSAID) used primarily as an analgesic and antipyretic.

From the chemical point of view, metamizole is a pyrazolone.

Examples of medicinal specialties containing metamizole

  • Metamizole Ratiopharm ®
  • Novalgina ®
  • Novazol ®
  • Piralgin ®

Metamizole - Chemical Structure

Indications

For what it uses

The use of metamizole is indicated for the treatment of febrile and / or severe and resistant states of pain.

Warnings

Metamizole can cause agranulocytosis (ie the severe decrease in the number of granulocytes circulating in the blood) or pancytopenia (ie, the decrease in the number of all blood cells). Therefore, if during the treatment with the drug, any of the following symptoms should occur, it is necessary to immediately stop the treatment and immediately inform the doctor who will prescribe appropriate analyzes and treatments:

  • Temperature;
  • Chills;
  • Sore throat;
  • Ulceration of the oral cavity;
  • General malaise;
  • Bruising;
  • Infections;
  • Pallor;
  • Bleeding;
  • Persistent fever.

Even if any type of allergic reaction appears, treatment with metamizole must be stopped immediately and the doctor must be contacted.

Because of the dangerous and serious side effects it can cause, metamizole should be used only when it is not possible to undertake different therapeutic strategies.

Interactions

Concomitant administration of metamizole and ciclosporin (an immunosuppressive drug) may result in decreased plasma levels of cyclosporine itself.

Concomitant intake of metamizole and methotrexate (an anticancer agent) may increase the toxicity of the blood induced by the latter.

Metamizole can reduce the effect of acetylsalicylic acid on blood coagulation. Therefore, caution should be used when administering metamizole in patients who are already taking acetylsalicylic acid in small doses.

When administered simultaneously, metamizole may decrease the plasma concentration of bupropion (an antidepressant).

In any case, it is always a good idea to inform your doctor if you are taking - or if you have recently been - drugs of any kind, including medicines without a prescription and herbal and homeopathic products.

Side effects

Metamizole can induce different types of side effects, although not all patients experience them. The type of adverse effects and the intensity with which they occur depend on the sensitivity that each individual has towards the drug.

The following are the main side effects that may occur during treatment with the drug.

Allergic reactions

Metamizole can trigger allergic reactions in sensitive individuals. These reactions can occur in the form of:

  • Itching, burning, swelling and / or redness of the skin and mucous membranes;
  • Urticaria;
  • Dyspnoea;
  • Gastrointestinal disorders;
  • Angioedema;
  • Severe bronchospasm;
  • Cardiac arrhythmias;
  • Circulatory shock.

Blood and lymphatic system disorders

Metamizole therapy may cause:

  • Piastrinopenia, ie the decrease in the number of platelets in the bloodstream;
  • Leukopenia, that is the reduction of the levels of leukocytes in the blood;
  • agranulocytosis;
  • Pancytopenia, with even fatal results;
  • Aplastic anemia.

Skin and subcutaneous tissue disorders

Treatment with metamizole may cause:

  • Skin eruptions;
  • Rash;
  • Stevens-Johnson syndrome;
  • Toxic epidermal necrolysis.

Kidney and urinary tract disorders

Metamizole-based therapy could cause:

  • Acute renal failure;
  • oliguria;
  • Anuria;
  • Proteinuria;
  • Acute interstitial nephritis.

Other side effects

Other side effects that could occur during treatment with metamizole are:

  • Kounis syndrome;
  • Isolated hypotensive reactions;
  • Pain at the injection site (when metamizole is administered parenterally);
  • Phlebitis (when metamizole is administered parenterally);
  • Red urine staining; this is due to the presence of a metamizole metabolite in the urine themselves.

Overdose

After overdose of metamizole, symptoms such as:

  • Nausea;
  • He retched;
  • Abdominal pain;
  • Impairment of renal function;
  • Acute renal failure;
  • dizziness;
  • Drowsiness;
  • Convulsions;
  • Coma;
  • Hypotension, sometimes up to the shock;
  • Tachycardia.

There is no specific antidote against metamizole hyperdosage. Gastric lavage, hemodialysis and administration of activated charcoal may be useful.

In any case, if you suspect a metamizole overdose, you must contact your doctor immediately and go to the nearest hospital.

Action mechanism

Metamizole exerts its analgesic and antipyretic action by inhibiting cyclooxygenase (or COX).

Cyclooxygenase is an enzyme of which three different isoforms are known: COX-1, COX-2 and COX-3.

The task of these enzymes is to convert the arachidonic acid present in our body into prostaglandins, prostacyclines and thromboxanes.

Prostaglandins - and especially prostaglandins G2 and H2 (respectively PGG2 and PGH2) - are involved in inflammatory processes and mediate pain responses. While type E prostaglandins (PGE) induce an increase in body temperature.

Metamizole, therefore, by inhibiting COX is able to prevent the synthesis of prostaglandins responsible for fever and pain.

Mode of Use - Posology

Metamizole is available for:

  • Oral administration in the form of oral drops or tablets;
  • Rectal administration in the form of suppositories;
  • Intravenous or intramuscular administration in the form of an injectable solution.

To avoid the occurrence of dangerous side effects, during treatment with metamizole it is essential to scrupulously follow the indications provided by the doctor, both as regards the amount of drug to be used, both as regards the frequency of administration and the duration of the same therapy .

The dose of metamizole usually used in adults and children over 15 years of age - when administered orally or rectally - is 500-1000 mg of drug, to be taken 3-4 times a day.

In children aged 4 to 14 years, however, the usual dose is 300 mg, to be taken up to three times a day.

Pregnancy and breastfeeding

Metamizole is able to cross the placenta and can cause serious damage to the fetus. Therefore, the use of the drug by pregnant women is not recommended, especially during the first and third trimester of gestation.

Metamizole is excreted in breast milk, therefore, breastfeeding should be avoided during the administration of metamizole and for a period of at least 48 hours from the same administration.

Contraindications

The use of metamizole is contraindicated in the following cases:

  • In patients with known hypersensitivity to the same metamizole or to other pyrazolones;
  • In patients with known hypersensitivity to pyrazolidines (such as, for example, phenylbutazone);
  • In patients who manifest - or have experienced - anaphylactoid reactions to other non-steroidal analgesic drugs (such as, for example, acetylsalicylic acid, ibuprofen, diclofenac, indomethacin, naproxen, etc.);
  • In patients with pre-existing agranulocytosis;
  • In patients with pre-existing bone marrow function impairment;
  • In patients suffering from pathologies of the hemolymphopoietic system;
  • In patients with acute intermittent porphyria;
  • In patients with a deficiency of the enzyme glucose-6-phosphate dehydrogenase;
  • In infants with less than three months of life or with a body weight of less than 5 kg;
  • Pregnant.

Furthermore, the use of intravenous metamizole is contraindicated in hypotensive patients or with circulatory instability and in infants from 3 to 11 months of life.

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