Purpose of the NICE guidance: to target zanamivir to at-risk patients with a high likelihood of having influenza. Hence the restriction to use in such patients and only when the level of circulating influenza-like illness has been confirmed to be above 50/100,000. Fever of over 38°C and a clinical picture of flu (sudden onset of illness with muscle pains and dry cough) are also a requirement before treatment with zanamivir is considered as many people think they have flu when they have much milder viral illnesses.
Benefits of the treatment: very modest with only a single day reduction in duration of illness and 7% reduction in complications requiring antibiotics. In other words 14 patients need to be treated with zanamivir for one patient to avoid the need for antibiotics. No proven benefit in terms of reducing hospital admission or mortality. (See picture below.)
Side effects: zanamivir can cause wheezing in asthmatic and COPD patients, so such patients are advised to have their reliever inhaler to hand when they take the treatment! In a study in healthy asthmatics one in 13 developed wheezing.
Children: zanamivir is not licensed for children under 12
Workload: NICE recognise that there could be a considerable extra workload caused by this guidance (in terms of telephone calls and home visits). Practices may wish to have a plan prepared to deal with this eventuality. A possible scenario would be 2 extra visits per GP per day with an unknown extra number of telephone calls for patients enquiring about their suitability for treatment. A questionnaire has been prepared for nurses to use in triaging telephone queries from patients and presumably this will be used by NHS direct, but could also be implemented at practice level. However issuing of prescriptions for zanamivir without seeing the patient seems unwise, in view of the possibility of complications (such as pneumonia), and the fact that it was a new ‘black triangle’ medication.
Cates plot on preventing complications of flu by using zanamivir
If 100 patients are all given zanamivir for a flu-like illness 74 will not suffer a complication requiring antibiotics anyway (shown as green smiling faces below); 20 will still need antibiotics (shown as red faces) and 6 (shown as yellow faces) will be saved from having antibiotics by the use of zanamivir.
Appendix 1
Summary of Nice Guidance on the Use of Zanamivir (Relenza) in the treatment of Influenza
Issue date: November 2000
Review date : June 2002
1. Guidance
1.1 For otherwise healthy adults with influenza, the use of zanamivir is not recommended.
1.2 Zanamivir is recommended, when influenza is circulating in the community, for the treatment of at-risk adults, who present within 36 hours of the onset of influenza like illness (ILI) and who are able to commence treatment within 48 hours of the onset of these symptoms.
1.2.1 Based on the evidence from clinical trials, at-risk adults are individuals falling into one or more of the following categories:
age 65 years or over
chronic respiratory disease (including chronic obstructive
pulmonary disease and asthma) requiring regular medication
significant cardiovascular disease (excluding individuals with hypertension)
immunocompromised
diabetes mellitus
1.2.2 Community based virological surveillance schemes should be used to indicate when influenza is circulating in the community (see paragraph 5.4).
1.2.3 Effective targeting of zanamivir for the at-risk adult population with a high incidence of true influenza is essential to maximise both the clinical and cost effectiveness of this therapy.
1.3 The guidance does not cover the circumstances of a pandemic or a widespread epidemic of a new strain of influenza to which there is little
or no community resistance. In such circumstances, the Department of Health and the National Assembly for Wales might wish to consult the Institute on the need for supplementary guidance.