Oral contraceptive linked to blood clots

November 25, 2001

NEW YORK, Oct 26 (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.

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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