November 8, 2011

Higher Risk of Blood Clots with Birth Control

(Ivanhoe Newswire) — Drospirenone-containing oral birth control pills are linked to a significantly higher risk of blood clots, both deep vein thrombosis and pulmonary embolism, according to this study.

All oral contraceptives are associated with a higher risk of blood clots, but there is conflicting information about the risk of adverse events with drospirenone. Many previous studies have evaluated risks of second- and third-generation contraceptives, which both contain derivatives of testosterone. Israeli researchers undertook a study to determine the risk of venous and arterial blood clots in various oral contraceptive users. They looked at data on 329 995 women in Israel aged 12 to 50 years who received oral contraceptives between January 2002 and December 2008 and followed them until 2009. There were 431 223 total use episodes.

The researchers found an elevated risk of venous thrombotic events for drospirenone users compared with second- and third-generation contraceptives. Risk was highest in the early months of use. A noticeable trend was a major increase in prescribing drospirenone-combined contraceptives over the years and a decline in use of second-generation contraceptives. Drospirenone has been marketed as causing less weight gain and edema than other birth control pills.

"Use of drospirenone-containing combined oral contraceptives was associated with a significantly increased risk of venous thrombotic events (deep vein thrombosis and pulmonary embolism) but not arterial thrombotic events (transient ischemic attack and cerebrovascular accident), relative to use of second- or third-generation combined oral contraceptives," Dr. Naomi Gronich, Pharmacoepidemiology and Pharmacogenetics Unit, Department of Community Medicine and Epidemiology, Office of Chief Physician, Clalit Health Services Headquarters, Tel Aviv, Israel, was quoted as saying.

Older age, high blood pressure, high cholesterol, cancer and obesity were also risk factors for blood clots.

"With the increasing use of drospirenone-containing contraceptives, it is important to raise awareness of the increased, albeit small, risk of venous thromboembolism relative to third-generation pills, especially among those who are older or obese," the authors were quoted as saying.

SOURCE: Canadian Medical Association Journal, published online November 7, 2011