Metamizol - a New Effective Analgesic with a Long History: A Survey of Pharmacology and ClinicalApplications

Overview

Metamizol is an effective, non-opioid analgesics which was originally introduced to the therapy in the year 1922.However, with the reference to the side effects of other related pyrazolone derivatives its administration, similarlyas the usage of other pyrazolones, was significantly limited. Later, metamizol has been used, usually mixed, withspasmolytic agents and quite recently it has been introduced as a mono-component medicament. Metamizol provedto be a very effective analgesic. When administered in equipotent doses, it had its effects comparable to variousopioid analgesics, such as tramadol, pentazocine and pethidine. Beside the strong analgesic effect, it produces alsosignificant antipyretic and splasmolytic effects without the adverse, unpleasant anticholinergic impact. Its spasmo-lytic effect on the smooth muscle of the sphincter Oddi, urinary tract, and the gal bladder is comparable to the effectsof buthylscopolamine. Unlike aspirin and other nonsteroidal antiinflammatory drugs it has, however, no antiinflam-matory activity when administered in clinical doses. Similarly, metamizol has no effect on the CNS, cardiovascularsystem, renal and metabolic functions. On the other hand, metamizol, like aspirin, has got a significant effect on theaggregation of platelets.Metamizol is basically a prodrug. The parent substance is not effective before its conversion into two activemetabolites (4-methylaninoantipyrine and 4-aminoantipyrine) in the body. Metamizol is well absorbed from thesmall intestine but only two above mentioned active metabolites and no parent drug can be detected in the blood.The active metabolites are consequently metabolised to ineffective metabolites including the relevant acetylderiva-tives, in which the acetylation phenotypes can be distinguished. In the therapy, metamizol can be used, as an analgesic,at post-surgical pain, patient’s controlled analgesia (PCA), at the cancer’s pain and in the pains of different origin(post-traumatic pain, the pain at myocardial infarction, craniocerebral trauma, and the invasive diagnostic interven-tions), as well as at he pain of neuromuscular origin, headache and migraine. Its spasmolytic effect in connectionwith a strong analgesic activity is very useful at various colic attacks. Further, metamizol is a useful antipyretic bothin the adults and children. Its adverse effects are not pronounced and drug interactions are minimal. Only whenmetamizol is administered together with cyclosporine, the blood levels of the last substance should be regularlychecked.

Key words:
metamizol, pharmacology, pharmacokinetics, therapeutic use.