Antitrust enforcers are investigating whether some pharmaceutical...

Antitrust enforcers are investigating whether some pharmaceutical companies are improperly claiming patent protection for their drugs to keep generic competitors off the market.

The probe by the Federal Trade Commission centers on whether some drug companies have wrongly listed their brand-name drugs in the “orange book,” a list of patent-protected drugs published by the Food and Drug Administration, an FTC spokeswoman said.

Among the drugs at issue are Bristol-Myers Squibb’s anti-anxiety drug, Buspar, and cancer drug Taxol, as well as GlaxoSmithKline’s antidepressant, Paxil, according to a report in USA Today.

A spokesman for Bristol-Myers said the company is cooperating with the FTC. Glaxo spokeswoman Mary Anne Rhyne said Paxil’s patents are properly listed in the orange book. She said the company also is cooperating with the FTC.