Use of antivirals in influenza in the elderly: prophylaxis and therapy.

Amantadine and rimantadine inhibit H1N1, H2N2, and H3N2 strains of influenza A, but not influenza B. Rimantadine exerts somewhat greater antiviral activity than amantadine, and there are several potentially important differences between the pharmacokinetic profiles and elimination pathways of the two drugs in favour of rimantadine. Adverse effects are more prominent in the elderly but can be minimized by dosage reductions. Both drugs are effective prophylactically and therapeutically and can be used for 'seasonal' prophylaxis, postexposure prophylaxis, outbreak control in residential care, and treatment during community outbreaks of influenza A. Drug-resistant strains of influenza have been recovered in up to half the subjects undergoing treatment, and prophylaxis may fail in homes where drug is given for both prophylaxis and therapy. Elderly residential patients and others identified by national immunization policies may benefit most from prophylactic administration of drug when influenza is first identified locally and for the duration of the outbreak.