Labels for oral contraceptives that contain drospirenone will now note that studies have shown as much as a threefold increase in risk of blood clots compared with other birth control pills, the FDA said.
Following a safety review that began last May, the agency "has concluded that drospirenone-containing birth control pills may be associated with a higher risk for blood clots than other progestin-containing pills."
The label changes apply to nine brand-name contraceptives -- Beyaz, Gianvi, Loryna, Ocella, Safyral, Syeda, Yasmin, Yaz, and Zarah -- and two generic formulations, all of which include 3 mg of drospirenone and either 0.02 or 0.03 mg of ethinyl estradiol.
Two (Beyaz and Safyral) also contain 0.451 mg of levomefolate calcium.
However, the FDA stopped short of declaring that drospirenone definitely increases risk of venous clotting on the basis of current clinical data.
"The studies reviewed did not provide consistent estimates of the comparative risk of blood clots between birth control pills that contain drospirenone and those that do not," the agency said in a Drug Safety Communication.
"The studies also did not account for important patient characteristics (known and unknown) that may influence prescribing and that likely affect the risk of blood clots. For these reasons, it is unclear whether the increased risk seen for blood clots in some of the epidemiologic studies is actually due to drospirenone-containing birth control pills," according to the statement.
Also, the FDA noted, the risk of clotting while using these products still appears to be lower than thrombosis risk during pregnancy and in the immediate postpartum period.
The agency provided the following estimates of the clotting risk for different groups of women, per 10,000 person-years:
- Nonpregnant women not using combination hormonal contraceptives: 1 to 5
- Combination contraceptive users: 3 to 9
- Pregnant women: 5 to 20
- Postpartum period (through 12 weeks): 40 to 65
Most of the data on which the FDA based its new position had been available last year, but the agency could not then decide whether the increased risk was real. The agency had asked for help from its drug safety and reproductive health drugs advisory committees at a joint meeting in December.
A slim majority of panel members -- 15 out of 26 -- said the benefits of drospirenone-containing contraceptives outweighed their risks.
But the committees voted overwhelmingly for more information on the products' labels.