Does the morning after pill contain a large dose of progesterone?

Emergency Contraception Pills Do Not Contain Large Doses of Progesterone

The morning after pill does not contain a large dose of progesterone, but rather contains either levonorgestrel (a progestin) or ulipristal acetate (a progesterone receptor modulator) that work primarily by delaying or inhibiting ovulation.

Types of Emergency Contraception

Emergency contraception (EC) is available in several forms:

1. Levonorgestrel-based EC

   • Contains a synthetic progestin (not natural progesterone)
   • Recommended dosage is a single 1.5 mg dose 1
   • Works primarily by delaying or inhibiting ovulation 1
   • Available as Plan B One-Step and generic versions

2. Ulipristal Acetate

   • A selective progesterone receptor modulator with both antagonistic and partial agonistic effects 2
   • Contains 30 mg of ulipristal acetate per tablet 2
   • More effective than levonorgestrel at the end of the 5-day window 1
   • May be more effective for women who weigh more than 165 pounds 1

3. Combined Estrogen-Progestin Pills (Yuzpe regimen)

   • Higher-dose combined oral contraceptive pills 1
   • Less preferred due to inferior side effect profile compared to levonorgestrel 1

4. Copper IUD

   • Most effective EC method (failure rate <1%) 1
   • Can be inserted up to 5 days after unprotected intercourse 1
   • Provides ongoing contraception 1

Mechanism of Action

Emergency contraception works through several mechanisms:

• Primary mechanism: Delaying or inhibiting ovulation 2

  • Levonorgestrel works by postponing follicular rupture but is ineffective when administered on the day of LH peak 3
  • Ulipristal acetate has a direct inhibitory effect on follicular rupture and can be effective even when administered shortly before ovulation 3

• Secondary mechanism: Possible alterations to the endometrium that may affect implantation 2

Effectiveness and Timing

• Emergency contraception is most effective when taken as soon as possible after unprotected intercourse 4
• Levonorgestrel EC is up to 85% effective in preventing pregnancy 1
• Ulipristal acetate maintains effectiveness throughout the 5-day window 1
• Copper IUD is the most effective form with a failure rate of less than 1% 1

Important Considerations

• Emergency contraception should not be confused with abortion pills; EC prevents pregnancy rather than terminating an established pregnancy 1
• Progestin-only emergency contraception pills should be avoided if BMI is greater than 30 kg/m² 1
• Drug interactions may reduce effectiveness of hormonal EC when taken with certain medications 1
• A condom should always be used concurrently with hormonal contraceptives for STI/HIV protection 1

Common Misconceptions

A common misconception is that emergency contraception contains large doses of hormones. In reality:

• Levonorgestrel EC contains 1.5 mg of a synthetic progestin 5, which is a relatively small dose compared to other hormonal medications
• Ulipristal acetate is a selective progesterone receptor modulator, not a high-dose progesterone 2
• Both medications have targeted effects on the reproductive system with minimal systemic impact when used as directed

Emergency contraception represents an important option for preventing unwanted pregnancy after unprotected intercourse, but it should not be considered an alternative to regular contraceptive methods due to its higher failure rate compared to consistent use of other contraceptive methods.