Tamiflu patients should be monitored, FDA says

WASHINGTON — Patients who take Tamiflu should be closely monitored for signs of abnormal behavior, health officials said Monday in announcing an updated label for the antiviral flu drug.

The added precaution comes after reports of more than 100 cases of delirium, hallucinations and other unusual psychiatric behavior in people treated with the drug, which is usually taken to prevent or lessen the severity of the flu.

The Food and Drug Administration said that a relationship between the drug and the behavior had not been established and that the updated label was "intended to mitigate a potential risk associated with Tamiflu." It recommends that close monitoring begin immediately after starting treatment with the drug.

Tamiflu's maker, Hoffman-La Roche Inc., said there was no evidence the drug caused the side effects. Both the company and the FDA noted that severe cases of the flu can spark the abnormal behavior flagged in the updated label.

Most cases involved children under 17 years old and came from Japan. The cases included three people who fell to their death after taking the drug, including one 14-year-old boy who climbed on the railing of his family's condominium, an FDA staff memorandum said.

The memorandum also cited the case of an 8-year-old who took one dose of Tamiflu and, about an hour and a half later, tried to run out of the front door of his home. The child would not answer to his name and was growling, according to the memorandum, which was prepared in advance of an FDA pediatric advisory committee meeting Thursday.

Dr. Debra Birnkrant, director of the FDA's division of anti-viral products, said it is uncertain if the abnormal behavior was caused by the drug or the flu. But she added: "Since there were a number of cases over the last year that we looked, we thought it would be the prudent thing to make the public aware."

Another drug for seasonal flu, amantadine, also has been associated with neurological side effects, mostly in the elderly, Birnkrant said.

Hoffman-La Roche said in a statement that reports of psychiatric side effects from Tamiflu are rare.

"While any relative contribution of Tamiflu to these events is unknown, Roche is committed to working closely with the FDA to ensure that the product label accurately reflects the reports," the statement said.

According to the FDA's memorandum, 24.5 million prescriptions for Tamiflu were filled in Japan from 2001 through 2005. In the U.S., there were 6.5 million prescriptions over the same period.

Many governments, including the United States, have been stockpiling the drug to combat a possible outbreak of the H5N1 avian influenza. Although the virus mainly infects birds, there have been 153 deaths worldwide since 2003, according to the World Health Organization.