German drugmaker Bayer AG has filed a complaint against US group Warner Chilcott claiming infringement of patents with the sale of its contraceptive Lo Loestrin.

The filing, placed in the US District Court of Delaware, alleges that Warner's manufacture, use, offer for sale, and/or sale of its Lo Loestrin FE (norethindrone and ethinyl estradiol) oral contraceptive product infringes Bayer’s US Patent No. 5,980,940.

Bayer's patent, which was issued in November 1999, relates to a pharmaceutical combination preparation for hormonal contraception.

In the complaint, Bayer is looking for "injunctive relief and unspecified monetary damages", Warner said.

But the firm stressed that the complaint "lacks merit", and that it "intends to vigorously defend the litigation" with "a number of strong defenses to the allegations" Bayer has made.

A spokesperson for Bayer confirmed the pending litigation to PharmaTimes World News but declined to provide any further comment on it.