What is the efficacy of levonorgestrel (LNG) compared to ulipristal acetate (Ellaone) for emergency contraception when taken within 24 hours?

From the Guidelines

Ulipristal acetate (Ellaone) is more effective than levonorgestrel for emergency contraception when taken within 24 hours, with a pregnancy risk reduction of about 98% compared to 95% for levonorgestrel. When considering the efficacy of emergency contraceptives, it is essential to prioritize the most recent and highest quality studies. According to the study by 1, ulipristal acetate may be more effective than levonorgestrel formulations, especially for women who are overweight or obese.

Key Points to Consider

• Both levonorgestrel and ulipristal acetate are effective emergency contraceptives, but ulipristal acetate has a higher efficacy rate when taken within 24 hours after unprotected sex.
• Ulipristal acetate works by preventing or delaying ovulation, even when taken closer to ovulation, making it more effective than levonorgestrel in certain situations.
• The study by 1 suggests that ulipristal acetate has been shown to be more effective than the levonorgestrel formulation 3–5 days after unprotected sexual intercourse.
• It is crucial to consider the potential side effects of both medications, such as nausea, headache, and menstrual irregularities, when making a decision.

Recommendations

• For maximum effectiveness, ulipristal acetate should be taken as soon as possible after unprotected sex, ideally within 24 hours.
• Levonorgestrel can still be considered a viable option, especially if ulipristal acetate is not readily available or if the patient has specific preferences or concerns.
• Healthcare providers should discuss the benefits and potential side effects of both medications with patients to determine the best course of action for emergency contraception.

From the Research

Efficacy of Levonorgestrel (LNG) Compared to Ulipristal Acetate (Ellaone)

• The efficacy of levonorgestrel (LNG) compared to ulipristal acetate (Ellaone) for emergency contraception when taken within 24 hours has been studied in several clinical trials 2, 3, 4.
• A meta-analysis of two randomized clinical trials showed that ulipristal acetate had a pregnancy risk 42% lower than levonorgestrel up to 72 hours and 65% lower in the first 24 hours following unprotected intercourse 2.
• Another study found that ulipristal acetate prevented almost two thirds of pregnancies, whereas levonorgestrel prevented around 50% of expected pregnancies in women using the method within 72 hours 3.
• A systematic review of the available evidence found that levonorgestrel is highly effective for preventing unintended pregnancy, and that a single dose of 1.5 mg is not inferior in efficacy to the two-dose regimen 4.

Comparison of LNG and Ulipristal Acetate

• Ulipristal acetate has been shown to be more effective than levonorgestrel in delaying or inhibiting ovulation 2.
• The side effects of both methods are mild and similar, with frequent menstrual irregularities being the main side effect of levonorgestrel 4.
• The earlier the treatment is given, the more effective it seems to be, with both methods being highly effective when taken within 24 hours of unprotected intercourse 2, 4, 5.

Timing of Treatment

• The timing of treatment is critical, with both methods being more effective when taken as soon as possible after unprotected intercourse 2, 4, 5.
• A study found that the earlier hormonal emergency contraception is used, the more effective it is, with levonorgestrel and ulipristal acetate being effective up to 5 days after unprotected intercourse 5.