The safety of Bayer's oral contraceptive Yasmin has been called into question on the back of new research, published in the British Medical Journal, which suggests the pill's drospirenone component may present a higher risk of blood clots than levonorgestrel-based rivals.
In one study, researchers used the UK General Practice Research Database to look at women aged 15-44 years who had no major risk factors for venous thromboembolism (VTE) and were initiated on an oral contraceptive containing oestrogen in combination with either drospirenone or levonorgestrel between May 2002 and September 2009.
The results of the case-controlled analysis suggest that those taking the drospirenone contraceptive were three times more likely to develop non-fatal blood clots than those on levonorgestrel-based ones, adding to growing evidence that the combined oral contraceptive containing drospirenone carries a higher risk VTE, the researchers note.
Writing in the BMJ, they call for a systemic review on the issue, and suggest that, in the meantime, "as no clear evidence exists to show that the use of the drospirenone pill confers benefits above those of other oral contraceptives in preventing pregnancy, treating acne, alleviating premenstrual syndrome, or avoiding weight gain, prescribing lower risk levonorgestrel preparations as the first line choice in women wishing to take an oral contraceptive would seem prudent".
The findings were echoed by a separate study also published in the BMJ based on US claims data, which showed the risk of non-fatal VTE among users of contraceptive pills containing drospirenone to be twice as high as levonorgestrel.
But Bayer was quick to defend the safety profile of its Yasmin franchise. It argues that the study methodology reported in these two publications "show significant flaws and the databases used provide less reliable conclusions than are available from existing scientific evidence".
“Clinical data from a period of more than 15 years and up to 10 years of post-marketing safety study results support Bayer’s assessment that its drospirenone-containing [contraceptives] are safe and effective when used as indicated and that the risk of VTE is similar to any other low-dose estrogen [pill] studied, regardless of the progestogen,” said Ilka Schellschmidt, Head Global Medical Affairs Women's Healthcare at the company.