Zanamivir (RelenzaŽ) (PDF Version)
Zanamivir is a neuraminidase inhibitor.
Zanamivir has more active against influenza A than B.
Zanamivir is a reversible competitive inhibitor of influenza neuraminidase. Virion release from infected cells and spread with the respiratory tract are inhibited due to blockade of this enzyme.
In vitro resistance to zanamivir occurs from mutations in either the hemagglutinin or neuraminidase genes, or both.
Zanamivir has low absolute oral bioavailability. The mean bioavailability after oral inhalation of zanamivir powder is 2 to 8 times greater than after ingestion. It has low plasma protein binding, ranging from less than 1 to 14% for concentrations from 10 to 0.05 mg/L. Zanamivir is almost exclusively eliminated from the body via the kidney and undergoes no metabolic biotransformation.
Bronchospasm is the most common adverse effect.
Powder for inhalation 5mg
Adults and children > 7 years of age and adults:
Two inhalations of 5mg each twice daily for 5 days (initiated within 48 hours of the onset of symptoms)
Disease state based dosing:
Renal Impairment: No dose adjustment necessary
Hepatic Impairment: No dose adjustment necessary
Contraindications/Warnings/ Precautions:
No data are available to support safety or efficacy in patients who begin treatment after 48 hours of symptoms.
There are no documented clinically significant drug interactions with zanamivir.
Category C: Risk unknown. Human studies inadequate.
None.
Brand names/Manufacturer:
RelenzaŽ/GlaxoSmithkline