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When amantadine hydrochloride was first licensed by the Food and Drug Administration in 1966, it was specified for prophylaxis of Asian influenza. Many who have watched amantadine's tortuous path to widespread acceptance believe a basic problem lay in this initial licensing.
"Soon after the approval," recalls Marvin Paulshock, PhD, associate director of clinical research, Biochemicals Department, the DuPont Company, "influenza underwent an antigen shift and we had the Hong Kong flu epidemic of 1968. The FDA decided that amantadine could not be promoted for Hong Kong influenza before its clinical effectiveness was proved. DuPont was able to show that the Hong Kong strain was inhibited by amantadine in vitro and in mice, but no clinical trials were established. We realized that we could never catch up—each time a trial would be completed, a new antigenic variant would have appeared."
Instead, DuPont waited while researchers abroad and in the United States
ZOLER ML. Amantadine's rocky road to acceptance. JAMA. 1983;249(8):991-992. doi:10.1001/jama.1983.03330320005002