Therapeutic efficacy of amantadine hydrochloride in patients with epidemic influenza A virus infection

: A virus infection was studied using half of the normal oral dose of amantadine hydrochloride-100 mg/d instead of 200 mg/d. The patients in this study, who visited the clinics during January and February 1999, were confirmed within 48 hours to have influenza A virus infections by the Directigen FluA test. Using a quasi-randomized controlled trial, 26 patients were treated with amantadine hydrochloride in addition to the usual medication, while 23 were treated with only the ordinary medication. There were no significant differences in the mean age, 35.6 years old, or in clinical features between the two groups. The period of fever over 38 degrees C in the amantadine treated group was 1 day while that in the control group was 1.7 days, which shows a significant difference (p = 0.049). There was no significant difference in the duration of aching, such as arthralgia, or of general fatigue. There was no significant difference in the appearance of subsequent new symptoms after the onset of influenza A virus infection. In conclusion, it is expected that oral amantadine hydrochloride, 100 mg/d, together with the ordinary medication, will reduce the duration of the period of fever over 38 degrees C.