Flu Drug Misuse Could Result in Drug Resistance

In the United States, the Food and Drug Administration (FDA) approved two antiviral drugs for treatment and prophylaxis of the 2009 H1N1 influenza virus: <"http://www.yourlawyer.com/topics/overview/tamiflu">Tamiflu (oseltamivir phosphate) and Relenza (zanamivir). Now, medical authorities are warning consumers to exercise caution when using these medications, says the LA Times. Tamiflu and Relenza should be used when necessary and must be used appropriately.

The U.S. Centers for Disease Control and Prevention (CDC) describes the swine flu as a new virus first detected in the U.S. in April 2009 that is spreading from person-to-person worldwide, probably in much the same way that traditional seasonal influenza spreads. The CDC said that as of June 11, 2009, the World Health Organization (WHO) indicated that a pandemic of the new H1N1 flu was underway.

Overuse or misuse of the drugs could pave the way for resistant strains of the emerging swine flu, which could make control of a pandemic all the more problematic, noted the LA Times. Meanwhile, a Tamiflu-resistant strain of Swine Flu was reported in Denmark this June. According to a prior Bloomberg.com report, Tamiflu drug maker Roche Holding AG said a patient treated with Tamiflu in Denmark exhibited drug resistance, the first time this has occurred in this outbreak. The LA Times notes that not only have some Tamiflu-resistant H1N1 cases been reported over the summer, but examples of drug misuse are occurring.

For instance, said the LA Times, citing a British report, people begin, but do not complete the full course of anti-viral treatment. This sort of misuse, or underuse, can lead to drug resistance. So can giving the medication to people who are not ill, as has been the case in some summer camps in the U.S., said the LA Times.

“Influenza viruses mutate frequently and any viral resistance could be acquired easily,” said Dr. Anne Schuchat, director of the National Center on Immunization and Respiratory Disease at the CDC, quoted the LA Times. “It won’t surprise us if we see resistance emerge as a bigger problem in the fall or in the years ahead,” Dr. Schuchat added.

Because vaccines for the Swine Flu are not available and are undergoing trials, Tamiflu and Relenza will be the primary forms of treatment against the pandemic. Meanwhile, the WHO is advising physicians that the medications not be given to “mildly or moderately sick” patients and patients not in high-risk groups, such as young children, pregnant women, and patients with other medical conditions, said the LA Times.

According to Dr. Robert Schechter, acting chief of the immunization branch of the California Department of Public Health, “These medicines can be very helpful to those who could get very sick.… But excessive use will accelerate the development of resistance and lead to the lack of a medication for everybody,” the LA Times quoted.

Although other antiviral medications are on the market, the Swine Flu is resistant to those in the adamantane class of drugs, noted the LA Times. If the virus becomes resistant to Tamiflu, then the only medication currently available to treat Swine Flu will be Relenza. But, Relenza is prescribed for ages five and above, noted Schechter, while Tamiflu, which is an inhaled powder, is not appropriate for the seriously ill or those with breathing problems, said the LA Times. “The more choices you have, the better for treatment,” Schechter said. “To lose any one of those options would pose great challenges for treatment of those who are most vulnerable or likely to die,” reported the LA Times.

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