Efficacy and safety of low dosage amantadine hydrochloride as prophylaxis for influenza A.
The efficacy and safety of prophylactic low dose amantadine hydrochloride was assessed in two double-blind, placebo-controlled, randomized studies. In a study of 476 subjects aged 18 to 55 years, adverse reactions were not significantly different between the group receiving 100 mg/day amantadine and the placebo group but significantly greater in the group given 200 mg/day (P less than 0.009). The influenza attack rate in this study was too low to assess efficacy. In an experimental challenge study of influenza A/Beth/1/85 in 78 subjects of similar age the prophylactic administration of 50 mg, 100 mg or 200 mg/day doses of amantadine were more effective than placebo in preventing influenza illness (P less than 0.02, 66, 74 and 82% protection, respectively), and in suppressing viral replication (P = 0.02). There was no significant difference between amantadine groups in influenza illness or viral shedding. Compared with the placebo group the 100 and 200 mg amantadine groups showed a significant decrease in infection rate (100 mg: 40% protection: P = 0.012; 200 mg: 32% protection: P = 0.045) whereas the 50 mg group did not (20% protection: P = 0.187). These results suggest that 100 mg/day of amantadine will reduce toxicity but maintain the prophylactic efficacy seen with 200 mg/day.
Reuman
P D
PD
James N. Gamble Institute of Medical Research, Cincinnati, Ohio 45219.
Bernstein
D I
DI
Keefer
M C
MC
Young
E C
EC
Sherwood
J R
JR
Schiff
G M
GM
D000293:Adolescent; D000328:Adult; D000547:Amantadine / Q000009:adverse effects / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D009980:Influenza A virus / Q000187:drug effects / Q000302:isolation & purification; D007251:Influenza, Human / Q000517:prevention & control*; D008875:Middle Aged; D010919:Placebos; D011897:Random Allocation; D013997:Time Factors; D014779:Virus Replication / Q000187:drug effects
D010919:Placebos; D000547:Amantadine