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Directive to use more Tamiflu stirs concern

The Centers for Disease Control and Prevention's unexpected recommendation that doctors begin prescribing Tamiflu for everyday influenza could have far-reaching ripple effects, according to pharmaceutical and flu experts.

They warn it is likely to increase demand for the limited supplies of the drug, the only known preventive against avian influenza H5N1, and it may render the drug less useful by shortening the time until flu develops resistance against it.

And it could have serious implications for senior citizens, those most at risk for flu complications and death. Seniors who receive their drugs under Medicare could be deprived of the best available protection against flu's potentially fatal side effects, because fewer Medicare drug plans pay for Tamiflu than pay for the less expensive drugs it replaced.

The CDC said Saturday that physicians should cease prescribing two older drugs, amantadine (Symmetrel) and rimantadine (Flumadine), as protection against the worst side effects of flu because most of the flu now circulating in the country has become resistant and the drugs no longer work. To adequately protect against serious illness or death, physicians should substitute Tamiflu, CDC said.

Flu kills about 36,000 Americans each year; the elderly and those with asthma and chronic lung problems are at highest risk of illness or death.

CDC Director Dr. Julie Gerberding said the agency did not expect its directive to significantly increase Tamiflu use and that the nation has adequate Tamiflu, which has been in great demand by countries stockpiling it against avian flu.

The directive's timing may contribute to its having a muted effect, said Dr. David Fedson, a drug policy consultant and former pharmaceutical executive. "Flu has peaked in some parts of the United States already, and by the time this sinks into clinicians' attention, most of the season may have passed," he said.

The CDC has not officially characterized this flu season, but its weekly report of flu activity shows, as of Dec. 31, only seven states experiencing "widespread" flu, the highest ranking, with nine states seeing "local" flu, 27 showing "sporadic" flu and two states with no flu reported at all.

Increased use of Tamiflu is a two-edged sword, drug experts warned: It may prevent severe illness and deaths from seasonal flu, but as it is used more often, "it will push [seasonal] flu toward developing more drug-resistant strains," said Henry Miller, a Hoover Institution fellow at Stanford University and a former official of the Food and Drug Administration.

Tamiflu is already the most-prescribed drug for flu: 497,000 prescriptions were written for it in 2004, according to IMS Health, a pharmaceutical information and consulting company. But its demand has jumped this year amid fears of avian influenza, for which it is the only effective drug: From January through August 2005, 1,700,000 prescriptions were dispensed, four times the total for 2004, IMS Health said.

That spike in demand, coupled with numerous orders from national governments as preparation for pandemic influenza, has created concern that Tamiflu supplies will run short, but its manufacturer says there is no shortage risk: "We are confident in our ability to meet seasonal demand for Tamiflu," said Roche spokesman Terence J. Hurley.

According to drug experts, Roche has subdivided its Tamiflu supplies, holding back enough to meet commercial demand before filling government orders for pandemic preparation. One group that might lack access to Tamiflu lies much closer to home: With the switch from amantadine and rimantadine to Tamiflu, some seniors may be unable to get flu medication.

A review of Medicare-funded drug plans in Georgia that have posted their formularies on the federal government's www.Medicare.gov Web site shows that while 82 plans covered amantadine and 79 covered rimantadine, only 62 covered Tamiflu.