The European Commission has opened an antitrust investigation against Johnson & Johnson and Novartis that may have hindered the entry of generic versions of the former's pain killer fentanyl.

The probe deals specifically with the Netherlands and contractual arrangements between the US healthcare giant and Novartis' Sandoz unit. The commission says it "may have had the object or effect of hindering the entry on to the market of generic versions of fentanyl in the Netherlands".

J&J sold fentanyl patches (as Duragesic) as a pain-reliever for chronic pain, principally for cancer patients. The EC added that the opening of proceedings does not prejudge the outcome of the investigation but means it will "deal with the case as a matter of priority" so see of there has been a breach of utopian Union antitrust rules.

EU antitrust commissioner Joaquin Almunia said that "I regard this sector as a priority in terms of enforcement of competition rules given its importance for consumers and for governments' finances". He added that "pharmaceutical companies are already rewarded for their innovation efforts by the patents they are granted", so “paying a competitor to stay out of the market is a restriction of competition that the Commission will not tolerate".

The commission is already investigating a number of firms, including Servier, Lundbeck and Cephalon (which has just been acquired by Teva) and has been keeping a close eye on the pharmaceutical sector following an industry-wide probe which opened in 2008.