WASHINGTON — The contraceptive vaginal ring has fewer metabolic adverse effects than do oral contraceptives and may be a better alternative for insulin-resistant women, those with diabetes, and women with metabolic syndrome at increased risk for cardiovascular disease, Dr. Karen Elkind-Hirsch and colleagues wrote in a poster presented at the annual meeting of the American College of Obstetricians and Gynecologists.
Combined oral contraceptives remain the first line of treatment for women who desired birth control or cycle control with contraceptive steroids. Although much effort has been directed toward minimizing their potential thromboembolic and cardiovascular disease risks, much less attention has been given to their metabolic effects, wrote Dr. Elkind-Hirsch, scientific director of the Woman's Health Research Institute in Baton Rouge, La.
There is some evidence that oral contraceptives may aggravate insulin resistance and exert other untoward metabolic effects that might increase a woman's long-term risk for diabetes and heart disease. Delivering low-dose oral contraceptives via a nonoral route such as the vaginal ring might provide efficacy and good cycle control with less risk, they wrote.
To test this, the investigators randomized 30 women aged 18–40 years to either the vaginal ring or to a low-dose monophasic oral contraceptive for five continuous menstrual cycles. They tested the effects of both methods of birth control on carbohydrate metabolism, using insulin sensitivity indices derived from fasting and oral glucose tolerance tests.
All patients were similar with regard to age, weight, and metabolic parameters at baseline. However, by the end of the treatment period, the researchers noted that insulin sensitivity measured with a glucose tolerance test was significantly decreased in women taking the oral contraceptive pill, compared with women using the vaginal ring. The pill also significantly increased insulin resistance from baseline to after the treatment period when fasting levels alone were measured.
The study results confirm that low-dose oral contraceptives can adversely impact metabolic function, Dr. Elkind-Hirsch and her colleagues concluded. “So many women of reproductive age have insulin resistance or type 2 diabetes now,” she said in an interview. “What birth control can we put them on that will not make this worse?
“The other issue is obesity. When you give the contraceptive drug vaginally, you're right at the source, so you can give less. We don't have to go orally, thus bypass the liver, and the ring delivers the drug at a more steady state than the pill,”she added.
She added that the “women loved the ring. Everyone who had been randomized to the ring really loved it. There was no breakthrough bleeding, no matter how high their [body mass indexes] were. Not to get the breakthrough bleeding on such a low dose was very nice, and I think that was due to the steady-state vaginal delivery.”