Wyeth is facing a delay before it can bring its new oral contraceptive product Lybrel to the US market, after it was issued an ‘approvable’ letter by the Food and Drug Administration.

The FDA has requested more information from the company before it will show a green light to the product, and also wants to discuss the application with as advisory committee later this year before delivering a verdict.

The advisory committee meeting is expected to tackle a number of topics, including pregnancy rates among study participants, bleeding patterns and the discontinuation rate among women in trials of the product.

The questions raised by the agency are thought to relate in part to manufacturing quality control problems at Wyeth’s facility in Guyama, Puerto Rico, which makes Lybrel along with other products, including the company’s new antidepressant desvenlafaxine. Last month, analysts predicted that the problems at the plant could hold up approval of this product as well.

Among the violations detailed by the FDA in a warning letter include a failure to clean and maintain packaging equipment to prevent contamination, poor inspection procedures and failure to investigate incidents of contamination.

Lybrel (ethinyl estradiol and levonorgestrel) is a low-dose oral contraceptive that differs from other products on the market in that it is taken 365 days a year, with no placebo or pill-free intervals. This leads to an elimination of menstrual periods in women, and while this may be welcomed by some women, concerns have been raised about the long-term safety of the approach.

Lybrel has been predicted to have sales potential of around $150 million a year in the USA. It is also being developed for the European market under the Anya brand name.

Lybrel is considered an important new product for Wyeth’s oral contraceptive business, which is seeing declining sales in the face of strong competition from rival drugmaker Schering – soon to merge with fellow German group Bayer.

Wyeth’s contraceptive sales came in at $525 million last year, an 11% decline on 2004 levels.