Drug-hormonal contraception interactions

June 1, 2010

Medical advances have increased the number of chronically ill children who are surviving into adolescence and adulthood, and their interest in sex and sexual behavior mirrors that of healthy teen counterparts.

Key Points

Medical advances have increased the number of chronically ill children who are surviving into adolescence and adulthood, and their interest in sex and sexual behavior mirrors that of their healthy teen counterparts.1 Studies have shown that healthcare providers of patients with chronic diseases such as epilepsy are often unfamiliar with the common drug interactions between drugs used to treat the underlying illness and the contraceptive agents available on the market.2,3 Pediatricians must be able to inform patients about the efficacy of contraception when there is concomitant medication use, and they must be able to describe the risks and benefits of such therapy. Recent data from the Centers for Disease Control and Prevention's Youth Risk Behavioral Surveillance Survey (YRBSS) indicated that approximately 48% of high school adolescents report ever having sex, and 15% have had at least 4 partners in their lifetime,4 so it is important to discuss contraception with all teens, including those with a history of chronic disease.

Serum concentrations of estrogens and progestins in contraceptive medications may be decreased when these agents are used concomitantly with other therapies, which may result in contraceptive failure. Hormonal contraceptives may also increase or decrease the bioavailability of other medications being used by the patient. To provide optimal guidance to patients, it is important for providers to be aware of common interactions between hormonal contraceptives and other drug therapies.

SCENARIO 1

Pediatric providers caring for sexually active adolescent girls have a variety of hormonal contraceptive methods to choose from (Table 1).5 In addition to thinking through the many options for pregnancy prevention, the pediatrician must also ensure that Amy understands the potential fetal effects that may occur if she becomes pregnant while being treated with carbamazepine. Carbamazepine has been associated with fetal malformations such as neural tube defects, reduced head circumference at birth, developmental delay, and dysmorphic features.6,7 The Food and Drug Administration (FDA) classifies carbamazepine as risk category "D." This means that there is evidence of risk to the fetus, although potential benefits to the patient may dictate continued use of the drug during pregnancy.8

Given that Amy is already committed to an enhanced contraceptive plan, the next task will be describing the available options, the drug components and how they work to prevent pregnancy, potential adverse effects, and potential drug interactions with her antiepileptic medication. Most of the studies regarding drug interactions between hormonal contraception and antiepileptics have focused on combined oral contraceptives (OCs). The quality of available data on this subject is variable, as the information is derived from studies that have measured different outcomes and used varying numbers of participants. However, with the information available, let us consider Amy's case, starting with her current medications.