The relative potencies of anti-influenza compounds.

The relative potencies of some standard anti-influenza compounds have been examined in vitro by plaque reduction in calf kidney cells, and in vivo by reduction in virus titers of the lungs of infected mice. Strains belonging to the four subtypes H0N1, H1N1, H2N2, and H3N2 were employed to compare the activity of amantadine hydrochloride and ribavirin. In vitro for all strains except A/NWS/OO(H0N1) amantadine hydrochloride was 3-4 times more active than ribavirin. In vivo with sensitive strains amantadine hydrochloride produced a plateau effect at higher dose levels, but at lower dose levels was marginally more active than ribavirin. The sensitivity of A/Hong Kong/1/68 (H3N2) to amantadine hydrochloride, rimantadine hydrochloride, cyclooctylamine, and ribavirin was also investigated. In vitro rimantadine hydrochloride was similar in activity to amantadine hydrochloride and ribavirin, but cyclooctylamine was considerably less active. In vivo cyclooctylamine was active only at 150 mg/kg/day, whereas rimantadine hydrochloride produced a plateau effect over a range of concentrations from 9,12-150 mg/kg/day.