Allergan PLC has filed a lawsuit against New York-based Pfizer Inc. over costs related to opioid litigation faced by the Irish drugmaker, Reuters reported Aug. 2.

The lawsuit is related to the marketing and sale of Kadian, a type of morphine, in the years before Allergan acquired the rights to the drug.

Allergan said most of the lawsuits that seek to hold it accountable for contributing to the opioid crisis are related to the improper marketing of Kadian, with allegations in those suits going back to the mid-1990s.

Kadian was owned by Alpharma Pharmaceuticals Inc., which was acquired by King Pharmaceuticals LLC in 2008. Pfizer acquired King Pharmaceuticals in 2010, according to Reuters.

The rights to Kadian had to be sold off in order to gain the U.S. antitrust approval for King's acquisition of Alpharma. The rights were bought by Actavis PLC, which acquired Allergan in 2016 and took its name.

Allergan alleged that, under a 2008 agreement between Actavis and King Pharmaceuticals, Pfizer was required to pay for any damages relating to Kadian's marketing and sale before 2009.

The Irish drugmaker's unit Allergan Finance LLC, which filed the lawsuit, stated that Pfizer has rejected any responsibility to indemnify Allergan for the lawsuits that seek to impose liability for marketing and sale of Kadian, the news outlet reported.

Pfizer did not respond to Reuters' request for comment.

In the past few months, states across the U.S. have filed lawsuits against companies including Endo International PLC, Teva Pharmaceutical Industries Ltd., Johnson & Johnson and Mallinckrodt PLC alleging unlawful marketing practices for opioid drugs.