Schering AG’s US subsidiary, Berlex, said yesterday it has launched its new contraceptive Yaz in the USA on schedule.

Yaz drospirenone/ethinyl estradiol) is a member of Schering's world-leading Yasmin franchise of low-dose contraceptives, and is the first pill which combines the innovative progestin drospirenone and a low dose of ethinyl estradiol in a new dosing regimen of 24 days of active hormone pills and four days of placebo.

However, Schering is being sued by US drugmaker Warner Chilcott over the regimen used in Yaz, with the latter claiming that it infringes patents it holds that cover a rival product, Loestrin 24 Fe, that is scheduled to be launched this month. Warner Chilcott is seeking treble damages, costs and to have Yaz removed from the market.

Schering originally planned to introduce the medicine in the US last year but was knocked back by an approvable letter from the FDA. The company, currently in the throes of a merger with fellow German company Bayer, has predicted that Yaz’ sales could reach 200 million euros ($247m) at peak.

Oral contraceptives continue to be the most widely used method of birth control in the USA, and their use has steadily increased since 1995. According to a recent Gallup Survey, 36% of women aged 18-49 who use birth control take oral contraceptives, said Schering.