Population-based comparison of two regimens for emergency contraception: a pharmacoepidemiologic study

Hormonal emergency contraceptives (EC), commonly referred to as “”morning after pills,”” have the potential to prevent pregnancy before it starts. They can be used as a preventive measure after unprotected sex by women who do not have a routine contraceptive method in place, who experience contraceptive failure such as condom breakage, or who miss several oral contraceptive doses. With the goal of improving women’s access to ECs, pharmacists in British Columbia were granted authority by the provincial government in 2000 to prescribe ECs without a doctor’s prescription. After granting pharmacists EC prescriptive authority, the province saw a 102% increase in EC prescriptions. The most commonly used ECs are the Yuzpe regimen, containing estrogen and progestin, and the progestin-only levonorgestrel regimen. Previous research has suggested that the effectiveness of the Yuzpe and levonorgestrel regimens is 76% and 89%, respectively.. However, there is growing evidence that the effectiveness of ECs has been overestimated in clinical studies. Also, there have been no studies to date that measured the outcomes (pregnancy versus no pregnancy) among women who received ECs under conditions of routine use. Using anonymized health data from all women who sought ECs from pharmacists in British Columbia in 2001 and 2002, pharmacist and graduate student Dr. Vivian Leung is comparing pregnancy rates between the two regimens. The rates will be used to estimate the effectiveness of each regimen and evaluate whether their effectiveness differs significantly when used in the routine community care setting. Leung’s study will explore the health outcomes of ECs on a larger scale than ever before. Her work will contribute important knowledge to better inform women and clinicians of optimal EC use in the prevention of unwanted pregnancy.