France's competition authority fined U.S. health-care group Johnson & Johnson 25 million euros ($29.62 million) on Wednesday after it found the company had deliberately slowed market access to generic copies of its painkiller Durogesic.
Durogesic is sold as a skin patch to control ongoing moderate to severe pain and is often prescribed in cancer cases. It contains fentanyl, an opioid which, if misused, can lead to death by overdose.
The French Autorite de la Concurrence said J&J's Janssen had "repeatedly intervened" to block the approval processes in France of Durogesic's generic copies and disparaged them when in contact with doctors and other healthcare professionals.
Officials at J&J could not be immediately reached for comment.
The case was brought to the watchdog by German firm Ratiopharm, later acquired by Israel's Teva Pharmaceuticals, after Durogesic lost its patent in 2005.
In 2013, France's Sanofi was ordered to pay 40.6 million euros for disparaging generic competition to its Plavix blood thinner.