From the Guidelines
EllaOne (ulipristal acetate) is generally more effective than levonorgestrel for emergency contraception, especially when taken later after unprotected sex. This is based on the most recent and highest quality evidence available, which suggests that ulipristal acetate remains effective up to 5 days (120 hours) after unprotected intercourse with minimal decline in efficacy throughout this period 1. In contrast, levonorgestrel works best within 72 hours and its effectiveness decreases significantly after 24 hours. For timing comparison, EllaOne reduces pregnancy risk by about 98% when taken within 120 hours, whereas levonorgestrel reduces risk by about 95% within 24 hours but drops to approximately 58% if taken between 48-72 hours.
Some key points to consider when choosing between EllaOne and levonorgestrel for emergency contraception include:
- The mechanism of action: Levonorgestrel (typically 1.5mg as a single dose) works by preventing or delaying ovulation, while EllaOne (30mg as a single dose) both delays ovulation and may affect implantation 1.
- Weight considerations: EllaOne may be less effective in women weighing over 165 pounds, while levonorgestrel's effectiveness decreases in women over 155 pounds 1.
- Side effects: Both medications are generally well-tolerated, with similar side effects including nausea, headache, and menstrual irregularities 1.
- Accessibility: EllaOne typically requires a prescription in most countries, while levonorgestrel is often available over-the-counter, making it more immediately accessible despite its somewhat lower efficacy 1.
It's worth noting that the CDC supports advance provision of emergency contraceptive pills and highlights that ulipristal (Ella) may be more effective than levonorgestrel formulations after the first 72 hours and for women who are overweight or obese 1. Overall, the choice between EllaOne and levonorgestrel for emergency contraception should be based on individual patient needs and circumstances, with consideration of the timing of unprotected sex, weight, and accessibility of the medication.
From the FDA Drug Label
The primary efficacy analyses were performed on subjects less than 36 years of age who had a known pregnancy status after taking study medication In the comparative study, a similar effect was seen for the comparator emergency contraception drug, levonorgestrel 1.5 mg. For levonorgestrel, when used by women with BMI > 30 kg/m 2, the observed pregnancy rate was 7.4% (95% CI: 3.9,13.4), compared to the expected pregnancy rate of 4. 4% in the absence of emergency contraception taken within 72 hours after unprotected intercourse. In the ellagroup, 16 pregnancies occurred in 844 women aged 16 to 35 years when emergency contraception was taken 0 to 72 hours after unprotected intercourse The number of pregnancies expected without emergency contraception was calculated based on the timing of intercourse with regard to each woman's menstrual cycle; ellastatistically significantly reduced the pregnancy rate, from an expected 5.6% to an observed 1. 9%, when taken within 72 hours after unprotected intercourse.
The efficacy of levonorgestrel (LNG) compared to ulipristal acetate (Ellaone) for emergency contraception is as follows:
- Ulipristal acetate reduced the pregnancy rate from an expected 5.6% to an observed 1.9% when taken within 72 hours after unprotected intercourse.
- Levonorgestrel had an observed pregnancy rate of 7.4% (95% CI: 3.9,13.4) in women with BMI > 30 kg/m2, compared to an expected pregnancy rate of 4.4% in the absence of emergency contraception taken within 72 hours after unprotected intercourse. Key points to consider:
- Time of administration: Ulipristal acetate was effective when taken within 72 hours after unprotected intercourse.
- BMI: Both ulipristal acetate and levonorgestrel had reduced efficacy in women with BMI > 30 kg/m2. 2
From the Research
Efficacy of Levonorgestrel (LNG) Compared to Ulipristal Acetate (Ellaone) for Emergency Contraception
- The efficacy of ulipristal acetate is higher than that of levonorgestrel, especially when administered later than 72 hours after unprotected intercourse 3, 4.
- A meta-analysis suggests that ulipristal acetate may be more effective than levonorgestrel from day 1 and throughout the entire 5-day period following unprotected sexual intercourse 3.
- Ulipristal acetate has been shown to be more effective than levonorgestrel in delaying or inhibiting ovulation, with a pregnancy risk 42% lower than levonorgestrel up to 72 hours and 65% lower in the first 24 hours following unprotected intercourse 4.
- However, it is noted that oral levonorgestrel is slightly less effective than ulipristal, and is less effective in patients with a body mass index of more than 30 kg per m2 and if administered after 72 hours 5.
Comparison of Effectiveness
- Ulipristal acetate is effective in preventing pregnancies when administered within 120 hours of unprotected intercourse, while levonorgestrel is approved for use within 72 hours 3, 6.
- The copper intrauterine device is an effective method that can be used in emergency contraception until 120 hours after unprotected intercourse or when there is a risk of contraceptive failure 6, 7.
- It is recommended to use emergency contraception as soon as possible after unprotected intercourse, and to inform patients that it is not 100% effective 7.