WASHINGTON (Reuters) -- The Food and Drug Administration warned doctors Monday about fatal liver disease in some patients taking the drug Tasmar, made by Swiss-based Hoffman-La Roche to treat Parkinson's disease.

The FDA said in a statement that three deaths due to acute liver disease had led it and the manufacturer to alert doctors and recommend major changes in how it is used. The FDA approved the drug in January. Hoffman-La Roche is a unit of Roche Holding Ltd.

The FDA said a precise death rate was not known but about 60,000 patients had been given Tasmar worldwide, indicating a rate of about one reported death for every 20,000 patients taking the drug.

Parkinson's disease is a slowly progressing degenerative disorder of the nervous system that causes tremor, sluggish movement and muscle rigidity. It afflicts about 1 percent of people older than 50.

FDA said Tasmar's new labeling would now state that the drug should be used only in patients who do not respond to other available treatments.

Doctors are advised to monitor liver function every two weeks and withdraw treatment if the patient shows little benefit within three weeks of taking Tasmar.

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