Amgen Inc. and Johnson & Johnson may be required to change prescribing information and reduce the recommended dose of their top-selling anemia drugs due to potential health risks, federal regulators said Tuesday.

The U.S. Food and Drug Administration said the drugs Amgen’s Epogen and Aranesp as well as Johnson & Johnson’s Procrit may need to be prescribed in the lowest possible doses after recent studies revealed certain off-label uses could increase patient risk of stroke, heart attack and death.

A group of cancer drug experts will meet Thursday to advise the FDA. Epogen and Aranesp account for more than 47 percent of annual sales for the Thousand Oaks-based biotech firm. Aranesp is approved for treating anemia induced by chemotherapy and related to kidney dialysis.

Shares in Amgen lost 66 cents, or 1 percent, to $63.10 in afternoon trading Tuesday on the Nadsaq.