Contraceptive Linked to Blood Clots
NEW YORK (Reuters Health)
- Oral contraceptives that contain the synthetic hormone cyproterone
carry a heightened risk of blood clots, new research confirms.
Blood clots known as deep vein thromboses have been linked to
newer types of oral contraceptives--the so-called third-generation
birth control pills.
These pills differ from older versions in the type of progestin
they contain. Progestin is a female hormone, and oral-contraceptive
combinations contain some form of it plus a form of estrogen.
Cyproterone, which acts like progestin, has also been linked
to a higher blood clot risk in small studies. Because cyproterone
acts against male hormones called androgens, oral contraceptives
containing the drug have been given to women with serious acne
or abnormal hair growth--both androgen-related. Cyproterone is
not available in the US.
To confirm a link between the drug and blood clots, US researchers
looked at data on nearly 100,000 women taking oral contraceptives.
They found that while blood clots were rare, cyproterone-containing
pills carried a four-times higher risk compared with pills containing
the progestin levonorgestrel. Levonorgestrel is found in older
contraceptives known as second-generation birth control pills.
Catherine Vasilakis-Scaramozza and Dr. Hershel Jick, of Boston
University School of Medicine in Lexington, Massachusetts, report
their findings in the October 27th issue of The Lancet.
The researchers looked at data on more than 24,000 women with
prescriptions for low-dose estrogen contraceptives containing
cyproterone and 75,000 women who had received levonorgestrel-containing
pills between 1992 and 1999.
From 1992 on, 26 women suffered confirmed or ``probable'' deep
vein thrombosis. When the investigators considered other risk
factors such as body mass and smoking, they found that cyproterone
was linked to a fourfold increase in the risk of blood clots.
Deep vein thrombosis, also known as venous thromboembolism, occurs
when blood clots form in the veins. In some cases, these clots
may travel through the bloodstream and lodge in the lungs, where
they can cause a potentially deadly condition called pulmonary
embolism. Ten women in this study had a pulmonary embolism.
``Our study results,'' the authors conclude, ``accord with those
of previous small studies, which have shown an association between
use of oral contraceptives containing cyproterone and increased
risk of venous thromboembolism.''
SOURCE: The Lancet 2001;358:1427-1429.
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