Zanamivir

Zanamivir is a medication used to treat and prevent influenza caused by influenza A and B viruses. It is a neuraminidase inhibitor and was developed by the Australian biotech firm Biota Holdings. It was licensed to Glaxo in 1990 and approved in the US in 1999, only for use as a treatment for influenza. In 2006, it was approved for prevention of influenza A and B. Zanamivir was the first neuraminidase inhibitor commercially developed. It is currently marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation. Zanamivir is a medication used to treat and prevent influenza caused by influenza A and B viruses. It is a neuraminidase inhibitor and was developed by the Australian biotech firm Biota Holdings. It was licensed to Glaxo in 1990 and approved in the US in 1999, only for use as a treatment for influenza. In 2006, it was approved for prevention of influenza A and B. Zanamivir was the first neuraminidase inhibitor commercially developed. It is currently marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation. Zanamivir is used for the treatment of infections caused by influenza A and influenza B viruses, but in otherwise-healthy individuals, benefits overall appear to be small. It decreases the risk of one's getting symptomatic, but not asymptomatic influenza. The combination of diagnostic uncertainty, the risk for virus strain resistance, possible side effects and financial cost outweigh the small benefits of zanamivir for the prophylaxis and treatment of healthy individuals.As of 2009, no influenza has shown any signs of resistance in the US. Since then, genes expressing resistance to zanamivir were found in Chinese people infected with avian influenza A H7N9 during treatment with zanamivir. In otherwise-healthy individuals, benefits overall appear to be small. Zanamivir shortens the duration of symptoms of influenza-like illness (unconfirmed influenza or 'the flu') by less than a day. In children with asthma there was no clear effect on the time to first alleviation of symptoms. Whether it affects the risk of one's need to be hospitalized or the risk of death is not clear. There is no proof that zanamivir reduced hospitalizations or pneumonia and other complications of influenza, such as bronchitis, middle ear infection, and sinusitis. Zanamivir did not reduce the risk of self reported investigator mediated pneumonia or radiologically confirmed pneumonia in adults. The effect on pneumonia in children was also not significant. Low to moderate evidence indicates it decreases the risk of one's getting influenza by 1% to 12% in those exposed. Prophylaxis trials showed that zanamivir reduced the risk of symptomatic influenza in individuals and households, but there was no evidence of an effect on asymptomatic influenza or on other, influenza-like illnesses. Also there was no evidence of reduction of risk of person-to-person spread of the influenza virus.The evidence for a benefit in preventing influenza is weak in children, with concerns of publication bias in the literature. As of 2009, no influenza had shown any signs of resistance in the US. A meta-analysis from 2011 found that zanamivir resistance had been rarely reported. Antiviral resistance can emerge during or after treatment with antivirals in certain people (e.g., immunosuppressed). In 2013 genes expressing resistance to zanamivir (and oseltamivir) were found in Chinese patients infected with avian influenza A H7N9. Dosing is limited to the inhalation route. This restricts its usage, as treating asthmatics could induce bronchospasms. In 2006 the Food and Drug Administration (FDA) found that breathing problems (bronchospasm), including deaths, were reported in some patients after the initial approval of Relenza. Most of these patients had asthma or chronic obstructive pulmonary disease. Relenza therefore was not recommended for treatment or prophylaxis of seasonal influenza in individuals with asthma or chronic obstructive pulmonary disease. In 2009 the zanamivir package insert contains precautionary information regarding risk of bronchospasm in patients with respiratory disease.GlaxoSmithKline (GSK) and FDA notified healthcare professionals of a report of the death of a patient with influenza having received zanamivir inhalation powder, which was solubilized and administered by mechanical ventilation. In adults there was no increased risk of reported adverse events in trials. There was little evidence of the possible harms associated with the treatment of children with zanamivir. Zanamivir has not been known to cause toxic effects and has low systemic exposure to the human body. Zanamivir works by binding to the active site of the neuraminidase protein, rendering the influenza virus unable to escape its host cell and infect others. It is also an inhibitor of influenza virus replication in vitro and in vivo. In clinical trials, zanamivir was found to reduce the time-to-symptom resolution by 1.5 days if therapy was started within 48 hours of the onset of symptoms. The bioavailability of zanamivir is 2%. After inhalation, zanamivir is concentrated in the lungs and oropharynx, where up to 15% of the dose is absorbed and excreted in urine.