Adherence to Oral Contraception in Women on Category X Medications

BACKGROUND: Over 6% of women become pregnant when taking teratogenic medications, and contraceptive counseling appears to occur at suboptimal rates. Adherence to contraception is an important component in preventing unwanted pregnancy and has not been evaluated in this population. We undertook a pharmacy claims-based analysis to evaluate the degree to which women of childbearing age who receive Category X medications adhere to their oral contraception. METHODS: We evaluated the prescription medication claims for over 6 million women, age 18-44 years, with prescription benefits administered by a pharmacy benefits manager. Women with 2 or more claims for a Category X medication and 2 or more claims for oral contraception were evaluated in further detail. Adherence to oral contraception was measured by analyzing pharmacy claims. Multivariable logistic regression was performed to identify factors associated with adherence. RESULTS: There were 146,758 women of childbearing age who received Category X medications, of which 26,136 also took oral contraceptive medication. Women who received Category X medications were prescribed oral contraception (18%) at rates similar to others of childbearing age (17%). Women prescribed both Category X and oral contraception demonstrated adherence similar to the overall population. Age, class of Category X medication, number of medications, prescriber's specialty, and ethnicity correlated with lower adherence rates. CONCLUSIONS: Despite added risk associated with unintended pregnancy, many women who receive Category X medications have refill patterns suggesting nonadherence to oral contraception. Compared with all women age 18-44 years, women receiving teratogenic medications do not have better adherence to oral contraception. (C) 2010 Elsevier Inc. All rights reserved. . The American Journal of Medicine (2010) 123, 929-934