The prophylactic effectiveness of amantadine hydrochloride in an epidemic of Hong Kong influenza in Leningrad in 1969

The effectiveness of amantadine hydrochloride as a prophylactic against influenza was studied during an epidemic caused by viruses related to influenza A2/Hong Kong/1968 variants in Leningrad, USSR, early in 1969. In all, 8169 subjects, assigned to amantadine-dosed, placebo-dosed, internal control and external control groups, were assessed. The index of effectiveness of the prophylactic medication, based on clinical diagnosis, in subjects who took amantadine regularly was 1.95. When the clinical diagnoses were confirmed serologically the index of effectiveness for the amantadine compared with the placebo group increased to 2.7. A comparison of the medicated group with the non-medicated, non-isolated internal control group showed an index of effectiveness of 5.34. A daily dose of 100 mg of amantadine was associated with an increase of 1.14% in complaints of sleep disturbances but these had no effect on the working capacity of subjects.