A new drug appears to reduce the number of blood platelets in people who have potentially hazardous high levels of the clot-forming cells.

Too many platelets, a relatively rare condition known is thrombocytosis, can lead to unwanted blood clots that cause heart attacks and strokes. Like too few platelets, too many can also cause excessive bleeding. Thrombocytosis may also result from other diseases, such as leukemia.The drug, anagrelide, returned platelet levels to normal in 20 patients without harming other kinds of blood cells.

A report on the research, directed by Dr. Murray N. Silverstein of the Mayo Clinic, was published in a recent New England Journal of Medicine. In their report, the doctors concluded the new drug "appears promising."