LAUSR

OBJECTIVE To estimate the cost-effectiveness of ulipristal acetate (UPA) and levonorgestrel (LNG) emergency contraception (EC) on pregnancy prevention among combined oral contraceptive (COC) pill users with an extended pill-free interval. We accounted for the potential interaction of COCs and obesity on EC efficacy. METHODS We built a decision-analytic model using TreeAge software to evaluate the optimal oral EC strategy in a hypothetical cohort of 100,000 twenty-five-year-old women midcycle with a prolonged "missed" pill episode (8-14 days). We used a 5-year time horizon and 3% discount rate. From a healthcare perspective, we obtained probabilities, utilities and costs inflated to 2018 dollars from the literature. We set the threshold for cost-effectiveness at a standard $100,000 per quality-adjusted life-year. We included the following clinical outcomes: number of protected cycles, unintended pregnancies, abortions, deliveries and costs. RESULTS We found that UPA was the optimal method of oral EC, as it resulted in 720 fewer unintended pregnancies, 736 fewer abortions and 80 fewer deliveries at a total cost savings of $50,323 and 79 additional adjusted life-years. UPA continued to be the optimal strategy even in the case of obesity or COCs impacting UPA efficacy, in which a COC interaction would have to change efficacy of UPA by 160% before LNG was the dominant strategy. CONCLUSION Our models found that UPA was the dominant choice of oral EC among COC users with a prolonged "missed" pill episode, regardless of body mass index or an adverse interaction of COCs on UPA. IMPLICATIONS Ulipristal acetate is the dominant choice of oral emergency contraception among combined oral contraceptive users.