Oseltamivir

How it works

Its active metabolite inhibits the influenza neuraminidase enzyme, preventing release of newly formed virions from infected cells and limiting spread of the virus.

Prescribing in practice

• It is most effective when started as early as possible and within a short window of symptom onset, so prompt initiation in at-risk patients is key.
• The dose requires reduction in renal impairment as it is renally cleared — check renal function and consult the SPC.
• Neuropsychiatric events, including abnormal behaviour, have been reported particularly in children and adolescents, so advise carers to monitor for unusual behaviour.

Monitoring

No routine laboratory monitoring is needed beyond assessing renal function to guide dosing and watching for neuropsychiatric symptoms.

Counselling the patient

• Start the medicine as soon as possible after symptoms begin and complete the full course.
• It does not replace annual influenza vaccination.
• Watch for any confusion, agitation or unusual behaviour, especially in children, and seek advice if this occurs.

Evidence & guidelines

Oseltamivir is recommended by NICE for the treatment and prophylaxis of influenza in at-risk groups during periods of circulating virus.