The Difference: Progestin vs. Progesterone
It is a common misconception that emergency contraception (EC) pills contain progesterone. In reality, the most common oral ECs contain a synthetic version of the hormone, known as a progestin. Natural progesterone is not used in over-the-counter EC pills.
Levonorgestrel (Plan B, Take Action, My Way)
Levonorgestrel is a progestin that prevents pregnancy primarily by delaying or inhibiting ovulation. It is available over-the-counter without a prescription or age restriction in the United States.
- Administration: This type of EC is typically administered as a single tablet. An older approach involving two tablets taken separately was also used but is less common now.
- Timing: For best results, levonorgestrel should be taken as soon as possible after unprotected intercourse. It is generally considered effective for a period after intercourse, although effectiveness may decrease over time. The sooner it is taken, the more effective it is.
- Body Weight: For women with a higher body mass index (BMI), levonorgestrel may be less effective.
Ulipristal Acetate (ella)
Ulipristal acetate is a prescription-only EC that is a selective progesterone receptor modulator. It works by blocking the effects of progesterone and delaying ovulation.
- Administration: The administration for ella is a single tablet.
- Timing: Ella is generally considered effective for a longer period after unprotected intercourse compared to levonorgestrel. It is often considered more effective than levonorgestrel in certain time frames after intercourse.
- Body Weight: Ulipristal acetate may be a more effective option for women with a higher BMI than levonorgestrel.
The Older Yuzpe Method
The Yuzpe method is an outdated regimen that uses a combination of estrogen and progestin from standard birth control pills. It is less effective and causes more side effects, such as nausea, than modern EC methods. This method is now only recommended if other more effective options are unavailable.
- Administration: This method involves taking a specific number of combined oral contraceptive pills at a certain time after intercourse, followed by another administration later. The exact number of pills varies depending on the specific birth control pill brand and its composition.
Other Emergency Contraception Options
It is important to note that the most effective form of emergency contraception is the copper intrauterine device (IUD), which can be inserted within a specific timeframe after unprotected sex and provides long-term contraception. The progestin-releasing IUD can also be used as an emergency contraceptive.
Comparison of Emergency Contraception Pills
| Feature | Levonorgestrel (e.g., Plan B) | Ulipristal Acetate (ella) | Yuzpe Method (Combined Pills) |
|---|---|---|---|
| Active Ingredient | Levonorgestrel (progestin) | Ulipristal Acetate (progesterone modulator) | Estrogen + Levonorgestrel |
| Administration | Single dose (or two doses) | Single dose | Multiple pills, two administrations |
| Timing | Effective for a period after intercourse | Effective for a longer period after intercourse | Effective for a period after intercourse |
| Effectiveness | High, best taken promptly | High, maintains efficacy longer | Lower and with more side effects |
| Availability | Over-the-counter | Prescription only | Prescription only (via combined oral contraceptive pills) |
| Side Effects | Nausea, fatigue, headache, menstrual changes | Nausea, fatigue, headache, menstrual changes | High incidence of nausea/vomiting due to estrogen |
What to Consider After Taking Emergency Contraception
- Potential Side Effects: Common side effects include nausea, headache, dizziness, and fatigue. Nausea is more frequent with older, combined-pill methods.
- Next Menstrual Period: The timing of your next period may be altered. It could be earlier or later than expected.
- Return to Fertility: Fertility can return quickly. It is recommended to use a backup contraceptive method (e.g., condoms) for subsequent acts of intercourse in the same cycle. For ella users, hormonal contraception should not be used for a specific period after taking the pill.
- Follow-Up: If your period is significantly late, or if you have any concerns, perform a pregnancy test. Emergency contraception is not 100% effective.
Conclusion
While the term "progesterone pills" is often used casually, oral emergency contraception relies on synthetic progestins like levonorgestrel or selective progesterone modulators like ulipristal acetate. The number of pills depends on the specific product: typically one pill for over-the-counter levonorgestrel options (like Plan B One-Step) or one prescription pill for ella. It is crucial to choose the appropriate method based on the time elapsed since unprotected sex and to follow the administration instructions for maximum effectiveness. For anyone considering EC, discussing options with a healthcare provider is always recommended. For additional guidance, authoritative sources such as the CDC offer detailed information on emergency contraception.
