Two new studies in the British Medical Journal have found that women taking the birth control pills Yaz and Yasmin face twice the risk of blood clots as those who are prescribed another contraceptive pill. The two studies found the increased blood clot risk also extended to other birth control pills that contain the hormone drospirenone (DRSP), including Ocella.

Because birth control pills containing DRSP can increase the amount of potassium in the blood stream, women who use these products also face an increased risk of other serious and potentially fatal side effects, including heart attack, stroke, deep vein thrombosis and other heart problem, as well as gallbladder disease, gallstones, kidney failure, liver failure, renal failure and pancreatitis.

At least 74 women who were injured after using Yaz or Yasmin have filed lawsuits against the manufacturers of these drugs, alleging that they were not properly warned about the risk they faced of blood clots and other side effects.

In October 2008, the Food and Drug Administration sent a warning letter to Bayer Pharmaceuticals, the manufacturer of Yaz, citing the company for running false and misleading advertisements for the birth control pills. The agency faulted Bayer for promoting Yaz as a treatment for acne and PMS symptoms—uses the FDA has not approved—and for understating the side effects risk associated with the birth control pills. Bayer was later forced to air a $20 million ad campaign to correct the misleading information in its original campaign.