Can Ella (ulipristal acetate) be used instead of Plan B (levonorgestrel) for emergency contraception?

Ella (Ulipristal Acetate) vs Plan B (Levonorgestrel) for Emergency Contraception

Ella (ulipristal acetate) is more effective than Plan B (levonorgestrel) for emergency contraception, especially when taken between 72-120 hours after unprotected intercourse and for women who are overweight or obese. 1, 2

Comparative Effectiveness

Timeframe Considerations

• 0-72 hours after intercourse:

  • Ulipristal acetate prevents approximately 85% of expected pregnancies 2
  • Levonorgestrel prevents approximately 75-80% of expected pregnancies 2
  • Meta-analysis showed ulipristal acetate has a 42% lower pregnancy risk than levonorgestrel within 72 hours 3
  • In the first 24 hours, ulipristal acetate has a 65% lower pregnancy risk than levonorgestrel 3

• 72-120 hours after intercourse:

  • Ulipristal acetate remains effective up to 120 hours (5 days) 2, 4
  • Levonorgestrel's effectiveness significantly decreases after 72 hours 2
  • Clinical trials showed no pregnancies when ulipristal acetate was administered more than 72 hours after intercourse 4

Body Weight Considerations

• For women with BMI > 30 kg/m²:
  • Ulipristal acetate: 3.1% observed pregnancy rate 4
  • Levonorgestrel: 7.4% observed pregnancy rate 4
  • Ulipristal acetate is preferable for women weighing more than 75 kg or with BMI > 25 kg/m² 5

Mechanism of Action

• Ulipristal acetate (Ella):

  • Selective progesterone receptor modulator 4
  • Can delay or inhibit ovulation even 24-48 hours before expected ovulation 6
  • Primary mechanism is inhibition/delay of ovulation; may also affect endometrium 4

• Levonorgestrel (Plan B):

  • Progestin-only emergency contraceptive 3
  • Less effective at delaying ovulation when taken close to ovulation 6

Safety Profile

• Both medications have similar side effect profiles 7, 8
• Common side effects include:
  • Headache (approximately 19% for both medications) 8
  • Nausea
  • Breast tenderness
  • Delayed menses by 2-3 days 7

Practical Considerations

• Prescription requirements:

  • Ulipristal acetate (Ella) requires a prescription 3
  • Levonorgestrel (Plan B) is available over-the-counter for all ages 5

• Subsequent hormonal contraception:

  • After using Ella, wait at least 5 days before starting hormonal contraception 4
  • Use a reliable barrier method until the next menstrual period 4

Clinical Decision Algorithm

1. If within 120 hours of unprotected intercourse:

   • First choice: Ulipristal acetate (Ella), especially if:
     • More than 72 hours have passed
     • Patient has BMI > 25 kg/m²
     • Close to expected ovulation

2. If within 72 hours and normal BMI:

   • Either medication is effective, but ulipristal acetate has slightly better efficacy

3. If no prescription access is available:

   • Levonorgestrel (Plan B) is appropriate if within 72 hours

4. For maximum effectiveness:

   • Consider copper IUD (>99% effective) if appropriate for the patient 2

Important Caveats

• Neither medication is effective if taken after ovulation has already occurred 5
• Both medications should be taken as soon as possible after unprotected intercourse 2
• The CDC supports advance provision of emergency contraceptive pills 1, 2