New study on risk of blood clots in women using hormonal contraceptives
A new major Danish registry study has investigated the risk of blood clots in women using different types of hormonal contraceptives. The study concludes, among other things, that women using a vaginal ring (Nuvaring®) or contraceptive patch (Evra®) have the highest risk of blood clots.
The absolute risk of blood clots is, however, still low. The study reveals an increase from around two cases of blood clots annually per 10,000 women not using hormonal contraceptives to around 8-10 cases of blood clots annually per 10,000 women using vaginal rings or contraceptive patches.
In February 2012, the Danish Health and Medicines Authority (the former Danish Medicines Agency) published a memo on the risk of blood clots associated with the use of contraceptive pills. The memo concluded that first and second-generation contraceptive pills are those associated with the lowest risk of blood clots. This conclusion still applies.
Number of users and cases of blood clots reported to the Danish Health and Medicines Authority's adverse reaction database
As can be seen from the chart below, the number of women using vaginal rings has shown an increase in recent years. However, the group of women using vaginal rings and contraceptive patches is still small compared with the number of women using contraceptive pills.
A few cases of blood clots have been reported as suspected side effects of vaginal rings and contraceptive patches to the Danish Health and Medicines Authority. The Authority’s adverse reaction database thus contains six cases of blood clots in women using vaginal rings and two cases of blood clots in women using contraceptive patches. In comparison, the recently published memo from the Danish Health and Medicines Authority on contraceptive pills showed that, over the years, more than 800 cases of suspected blood clots from the use of oral contraceptives have been reported.
Next step for the Danish Health and Medicines Authority?
The product information for the vaginal ring and the contraceptive patch is very comprehensive, but mainly contains general information about the risk of blood clots associated with the use of hormonal contraceptives. The risk is also stated in the package leaflets for the medicinal products. The package leaflet for the contraceptive patch states that the risk of blood clots may be higher than that associated with contraceptive pills. The current package leaflet for the vaginal ring states that the risk of blood clots from using hormonal contraceptives is increased, but that the risk of using a vaginal ring compared to that of contraceptive pills is unknown.
Based on the new study, the Danish Health and Medicines Authority will raise the issue in the EU Pharmacovigilance Working Party (PhVWP) to discuss, at an overall level, whether further and stricter measures are required in the product information for the medicinal products.