Two studies into Bayer’s best-selling contraceptives Yasmin and Yaz have shown that women on the medicine run a higher risk of getting dangerous blood clots than those using older pills.
The studies show that those using pills containing drospirenone, a hormone in Yasmin, have a threefold risk of venous thromboembolism that those using pills containing synthetic hormone levonorgestrel, according to the British Medical Association’s Bmj.com site.
Thromboembolism is the term for a blood clot in the veins — mostly in the legs — which becomes dislodged and can cause clogging in the lungs’ arteries.
Researchers described the overall risk as low with rates about 30.8 per 100 000 women on drospirenone.
Bayer has lashed out, saying the methodology of the studies was flawed.
“Given the already large and robust scientific body of evidence, in Bayer’s opinion, these studies do not change the overall assessment about the safety of Bayer’s oral contraceptives,” the company said. Bayer cited 10 years of safety studies since Yasmin entered the market.
Inconsistent results
Studies in recent years have yielded inconsistent results with some showing elevated risk and others finding that drospirenone is as safe as levonorgestrel.
Bayer last year added risk warning on the label but said the risk profile remained unchanged.
In the company’s 2010 report, it was stated that around 6 850 lawsuits were pending in the US with plaintiffs claiming they had suffered negative results from Yasmin and Yaz or generic copies sold by Teva’s Barr Laboratories.
Bayer experienced a 13% drop in sales of drospirenone-based pills like Yasmin, however, remaining Bayer’s second best-selling pharmaceutical product behind multiple sclerosis drug Betaseron.
The drop in sales has been attributed to the entrance of generic medication in the US and also because of the increased risk of thrombosis.