drug therapies
Antiviral Agents for Influenza A Current Treatments |
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| Two compounds, amantadine hydrochloride and rimantadine hydrochloride, show specific antiviral activity against influenza A. These agents block the replication cycle of type A influenza viruses. The drugs are recommended for long-course use as a prophylactic in high risk populations (HIV+ persons, persons for whom influenza vaccine is contraindicated, health care workers of those of high risk) and/or during outbreak. They are also used in short-course drug therapy for persons with active infections. |  Rimantidine & Amantidine: Image from National Foundation for Infectious Diseases |
| Amantadine was approved for use in prophylaxis and therapy for
adulsts in 1976, and Rimantadine was approved in 1993 for therapy and prophylaxis in
adults and prophylaxis in children over 1 years old. When administered as a prophylactic
before and throughout the epidemic period, both drugs are 70%-90% effective in preventing
clinical illness against most wild type strains (not necessarily infection). As a
treatment, both drugs can reduce the severity of clinical infection if administered within
48 hours of illness onset. Drug resistant viruses have been isolated from individuals receiving Amantadine or Rimantadine treatment; controlling the emergence and transmission of drug-resistant strains is a major consideration of the health industry. The Advisory Committee on Immunization Practices (ACIP) endorses the selective application of drug therapy and encourages patients on Amantadine and Rimantadine to avoid contact with uninfected persons. Persons with symptomatic immune deficiencies are particularly prone to harboring drug resistant strains through drug therapy. Chemoprophylaxis may be an effective measure to preventing disease and resultant drug-resistant strains.
A new class of drugs for Influenza A is under investigation, one based on influenza neuraminidase (NA)
inhibitors. A particular NA inhibitor, Zanamivir (relenza), has proven its efficacy
both in prophylaxis and in therapy. Zanamivir can be delivered as a nasal spray or
topically in the intranasal region. Studies in vitro have shown that some strains of
influenza A with particular mutations are resistant to the activities of NA inhibitors
(their ability to replicate, however, was also compromised). |
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Zanamivir: R & D Insight Profile |
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Zanamivir Press Release |
New Treatments