Zanamivir in the treatment of influenza

Influenza is a common illness, affecting many people every winter, with a considerable impact on mortality, hospital admissions, healthcare utilisation and sickness absence from work and school. Influenza management is currently focused on annual vaccinations for those in certain risk groups. Risk is determined by age and chronic illness, particularly diabetes, chronic respiratory and cardiac disease, and persons immunocompromised from disease or concomitant therapy. Amantadine (and in some countries, rimantadine is available but has not been widely used, because it is only effective against influenza A infections. The use of amantadines for treatment has been associated with the rapid emergence of resistant viruses capable of transmission, compromising its potential as a prophylactic, as well as a treatment. Side effects are well recognised and are a particular problem in the most vulnerable elderly populations, where dose restriction is necessary and prior knowledge of creatinine clearance desirable. The potential market for a new influenza treatment is large and the potential role of neuraminidase inhibitors in addressing this market has been covered in several review articles [1-4]. This review reports on the introduction of zanamivir (Relenza) to the market with particular reference to experience in the UK.