Oseltamivir is an inhibitor of the influenza neuramidase enzyme and is used as therapy and prophylaxis against influenza A and B. Oseltamivir has not been associated with clinically apparent liver injury.
Oseltamivir (oh" sel tam' i vir) phosphate is an ester prodrug of an antiviral enzyme inhibitor which, after absorption, is converted in the liver to oseltamivir carboxylase, the active intermediate. Oseltamivir caryboxylase is a potent inhibitor of the enzyme neuramidase of the influenza virus particle. Inhibition of this enzyme causes a decrease in viral replication, probably as a result of interference with particle formation and release. Oseltamivir is active against both influenza A and B virus, but has no activity against other common upper respiratory tract viruses. In addition, resistance to oseltamivir can develop rapidly. Oseltamivir is indicated for therapy or post-exposure prevention of influenza A and B. Oseltamivir was approved for in the United States in 1999 and is commonly used during influenza outbreaks. Oseltamivir is available as capsules of 30, 45 and 75 mg and as an oral suspension (6 mg/mL) under the brand name of Tamiflu. The recommended oral dose for therapy in adults is 75 mg twice daily for 5 days; the usual prophylactic dose is 75 mg once daily for 10 days, starting within 2 days of close contact with an infected person. Side effects are uncommon and include mild nausea, gastrointestinal upset, dizziness and headache.
Despite widespread use, there is little evidence that oseltamivir when given orally causes liver injury, either in the form of serum enzyme elevations or clinically apparent liver disease. A proportion of patients with acute influenza A may have minor serum enzyme elevations during the acute illness, but these appear to be independent of therapy and are not exacerbated by osteltamivir.
Mechanism of Injury
Oseltamivir is metabolized by the liver to the active intermediate oseltamivir carboxylate, but has little further hepatic metabolism and is excreted largely in the urine. The typical course of oseltamivir is for 5 to 10 days only, and the brief exposure and minimal hepatic metabolism may account for the absence of hepatotoxicity.
REPRESENTATIVE TRADE NAMES
Oseltamivir – Tamiflu®
Product labeling at DailyMed, National Library of Medicine, NIH
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References updated: 24 January 2014
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