Metamizole at a Glance and in Practice – Effective Non-Opioid Analgesic for All Ages

Proven in Practice for a Century

Pharmacotherapy of pain represents a very extensive area where new drugs are constantly emerging. However, proven preparations with effects on acute pain (AP), which can also be used in certain cases for chronic non-cancerous (CNCP) and cancer pain (CP), have been preserved. Such drugs include metamizole, which was patented in Germany in 1922. This time frame is, in itself, proof of its quality, emphasized the speaker at the beginning.

Pharmacological Characteristics and Benefits

Metamizole is characterized by a pronounced analgesic effect, and it also serves as an antipyretic. Its anti-inflammatory activity is lower, but unlike other non-opioid analgesics, it has spasmolytic properties. It differs from other antirheumatics in the absence of adverse effects on the GIT. Another advantage is that it does not affect platelet aggregation. Therefore, it is suitable for patients with a history of gastropathy or those taking medications affecting blood clotting.

It is completely absorbed from the GIT, evenly distributed in body compartments, and its metabolites also have a significant analgesic effect. It reaches maximum plasma concentration within 30 minutes, at which time its effect begins.

Possible Combinations and Interactions

Metamizole can be effectively and safely combined with nonsteroidal anti-inflammatory drugs, paracetamol, weak and strong opioids, gabapentinoids, and antidepressants. The drug has only minimal drug interactions. Combination with chlorpromazine can cause hypothermia, with methotrexate it can cause hematopoiesis disorder, and when administered with cyclosporine A, mutual influence of concentrations can occur. Very rare risks include hematological risks, anaphylactic reaction, allergies, skin reactions, and hypotension.

Main Indications and Contraindications

The main indication area for metamizole is AP, including postoperative and post-traumatic pain. For visceral colicky pain, it is a first-line drug. In the case of CP, where opioids are the main drug, it can serve as rescue and supplementary medication. It has proved effective in many forms of AP that did not respond to previous pharmacotherapy and in exacerbations of CNCP and CP. It also acts on pain associated with flu-like illnesses, such as muscle, head, or joint pain. It can also be used in patients with COVID-19.

Contraindications include hypersensitivity to pyrazolone derivatives, allergic asthma, allergic reaction to nonsteroidal anti-inflammatory drugs, disorders of hematopoiesis including drug-induced (e.g., during chemotherapy), porphyria, pregnancy, and lactation.

Key Information at a Glance

In conclusion, MUDr. Lejčko emphasized that metamizole is an effective non-opioid analgesic with the potential to influence primarily nociceptive pain. It is a drug useful in the entire age spectrum. It is available in several dosage forms – oral drops, tablets, and as a solution for i.v. administration. Oral drops have the advantage of individualization and faster onset of effect; they can be used without age restriction. Adults can take up to 4 g (8 tablets) daily for short-term use. Long-term use should be monitored with blood tests and liver function tests. In the case of renal and hepatic dysfunction, dose reduction is necessary.

Questions and Answers

The final section, dedicated to questions and answers, opened with a topic on psychosomatic pain – whether to administer analgesics in these cases and to what extent metamizole is usable in this area.

The next question was whether the speaker had metamizole in an injectable form in his office and if he uses it. Dr. Lejčko answered that he provides a composite infusion with an opioid (e.g., morphine, corticosteroid, and metamizole) to patients with cancer-related pain exacerbation, rheumatic disease, and lumbago. He does not recommend intravenous injection application.

There were also questions on what type of pain to administer tramadol, on what type to use metamizole, when to choose the combination of these analgesics, and what the tolerance to this combination is like. The author stated that the tolerance is well-experienced. At the same time, he warned that tramadol, as an opioid, can cause nausea and, in the case of long-term use, dependence.

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Source: 

Lejčko J. Metamizole in Pain Treatment. Webinar of the General Medicine Society of ČLS JEP, March 25, 2021. Available at: www.praktickylekar.online/KvW-JQ0tKW4