Pharmacies are bracing for an increased demand for antiviral medications even as health officials warned that the drugs, designed for treating and preventing influenza, should be used judiciously.
Two of the four antiviral drugs in production, Tamiflu (oseltamivir) and Relenza (zanamivir), appear to be effective against the strain of swine flu circulating in the United States, and on Sunday, Homeland Security Secretary Janet Napolitano announced that the government would release 25% of its emergency stockpiles -- about 12 million doses -- of Tamiflu and Relenza to various states in case they were needed. However, many questions remain about how to best use the drugs.
Indiscriminate use may ultimately limit their effectiveness.
"The medications can treat people who are ill and people who are exposed, so they are a good weapon for dealing with whatever might happen," said Dr. Anne Moscona, an infectious-diseases specialist at Weill Cornell Medical Center in New York. "But I have serious concerns about misuse. There is a danger in using these drugs in a way that encourages the development of drug-resistant viruses."
Vaccination is the best approach to curbing a viral outbreak. But it would take about six months to create a swine flu vaccine, according to officials at the Centers for Disease Control and Prevention. (A swine flu vaccine has not yet been ordered into production, although a seed stock has been prepared.) Thus, antivirals are used to try to curb transmission in the early days of an outbreak.
The U.S. government began collecting the drugs, called the Strategic National Stockpile, in recent years as concerns grew over the emergence of dangerous viruses, such as the bird flu that has killed more than 200 in Asia.
"This is where the preparations we've made over the past few years because of avian flu will prove useful," Moscona said. "There is a strategy in place for this kind of situation."
Small supplies of the antivirals are usually stocked by pharmacies year-round. But even with the federal government's stockpile, not enough of the drugs are expected to be available should a swine flu pandemic occur.
Influenza viruses can become resistant to the drugs, so doctors should think carefully about how the drugs are prescribed if the swine flu outbreak widens, said Dr. John Flaherty, associate chief of infectious diseases at Northwestern University's Feinberg School of Medicine.
