For the initial treatment of active tuberculosis in adults and children when combined with other antituberculous agents.
Pyrazinamide is an important sterilizing prodrug that shortens tuberculosis (TB) therapy. However, the mechanism of action of pyrazinamide is poorly understood because of its unusual properties. In literature it has been written that the pyrazinoic acid (POA), the active moiety of pyrazinamide, disrupted membrane energetics and inhibited membrane transport function at acid pH in <i>Mycobacterium tuberculosis</i>. The antimycobacterial activity appears to partly depend on conversion of the drug to POA. Susceptible strains of <i>M. tuberculosis</i> produce pyrazinamidase, an enzyme that deaminates pyrazinamide to POA, and the vitro susceptibility of a given strain of the organism appears to correspond to its pyrazinamidase activity. Experimental evidence suggests that pyrazinamide diffuses into <i>M. tuberculosis</i> in a passive manner, is converted into POA by pyrazinamidase, and because of an inefficient efflux system, accumulates in huge amounts in the bacterial cytoplasm. The accumulation of POA lowers the intracellular pH to a suboptimal level that is likely to inactivate a vital target enzyme such as fatty acid synthase. Recent studies (2007) demonstrated that pyrazinamide and its analogs inhibit the activity of purified FAS I.
Side effects include liver injury, arthralgias, anorexia, nausea and vomiting, dysuria,malaise and fever, sideroblastic anemia, adverse effects on the blood clotting mechanism or vascular integrity, and hypersensitivity reactions such as urticaria, pruritis and skin rashes.
Rapidly and well absorbed from the gastrointestinal tract.
9-10 hours (normal conditions)
Approximately 70% of an oral dose is excreted in the urine, mainly by glomerular filtration within 24 hours