The influenza drug Tamiflu will now come with a new caution urging close monitoring of patients for abnormal behavior, such as delirium and self-injury, U.S. regulators said on Monday.

Officials felt it was important to add the information to the Tamiflu label even though it is not certain that the drug contributed to any of the more than 100 reports of psychiatric problems, the Food and Drug Administration said. Most cases, including some reported suicides, were recorded in Japan and involved children.

“Patients with influenza should be closely monitored for signs of abnormal behavior immediately after starting Tamiflu because reports of these events indicate they occurred after one-to-two doses,” an FDA statement said.

“The agency feels that the neuropsychiatric labeling revision provides important safety information and is intended to mitigate a potential risk associated with Tamiflu. The relative contribution of the drug to these events is not known,” the FDA added.

Countries around the world are stockpiling Tamiflu to use if an influenza pandemic erupts. Known generically as oseltamivir phosphate, Roche AG’s Tamiflu is FDA-approved for treating and preventing the flu in adults and children as young as 1 year old. The drug is available as a pill and a liquid.

Roche said it would add the new language. The company also said there was no evidence Tamiflu was responsible for the psychiatric problems, which Roche said were rare given its use by more than 42 million people since 1999.

“As it is possible for untreated flu sufferers to experience similar events, any relative contribution of oseltamivir is not known,” a Roche statement said.

The information about the mental problems reported will be included as a precaution in the prescribing instructions for Tamiflu. A precaution is a less-serious note on a drug label than a warning.

Concerns about psychiatric problems surfaced last year after 12 children in Japan were reported to have died and 32 experienced abnormal behavior after they took Tamiflu.

Since then, FDA reviewers evaluated 103 reports of psychiatric problems from August 2005 to July 2006, according to a summary posted on the FDA Web site on Monday. They included three deaths of patients who appeared healthy other than having the flu, the reviewers said.

Nearly all of the cases - 95 out of 103 - came from Japan, where Tamiflu is used more widely. Two thirds of the total occurred in patients younger than 17, the FDA staff said.

The FDA released the staff summary and the new label ahead of a Thursday meeting of an advisory committee of pediatric experts. The panel is scheduled to hear updates on the safety of Tamiflu and several other drugs given to children.