Rimantadine 100 mg should be given once daily, rather than the usual dosage of 100 mg twice daily.
A reduced dose of rimantadine is recommended for elderly patients. Amantadine may be used, but the incidence of side effects ranges from 10% to 20% or greater. The prophylactic dosage of oseltamivir is 75 mg daily; the dosage for treatment of influenza is 75 mg twice daily. Zanamivir has been shown to be effective for influenza prophylaxis in elderly patients.