Public Health England issues revised guidance on antiviral prescribing when A(H1N1)pdm09 influenza virus is the dominant circulating strain

Based on latest guidance from PHE, treatment recommendations for the management of severely immunocompromised patients have changed, advising the use of zanamivir instead of oseltamivir in these patients.

When H1N1 is the predominant circulating strain then there is an increased risk of development of oseltamivir resistance in patients who might need prolonged courses. Severely immunosuppressed patients often need prolonged courses because they have continual viral shedding due to innate inability to clear virus and the risk of developing resistance is higher. This has implications for their own treatment/prophylaxis outcome but also for potential onward transmission of resistant virus.

 

The revised guidance stipulates that as A(H1N1)pdm09 is known to be the dominant circulating virus this season, it is therefore recommended that zanamivir is prescribed as the first line antiviral for SEVERELY immunosuppressed patients, but not immunocompetent patients.

 

In severely immunosuppressed patients with complicated influenza, particularly those with critical illness, the systemically-active intravenous preparation of zanamivir (unlicensed) is preferred over locally-acting inhaled or nebulised preparations.