What Is Afterpill and How Does It Work?
Afterpill is an over-the-counter emergency contraceptive (EC) containing a high dose of the hormone levonorgestrel. It is a generic version of Plan B One-Step and works in the same way. Unlike routine birth control, it is a backup method to be used after contraceptive failure or unprotected sex, not as a primary form of contraception.
Afterpill's primary mechanism is to prevent pregnancy by delaying or inhibiting ovulation, which is the release of an egg from the ovary. If no egg is released, fertilization cannot occur. It is important to note that Afterpill does not terminate an existing pregnancy and is not an abortion pill.
The Afterpill Success Rate Depends on Timing
For levonorgestrel-based pills like Afterpill, timing is the most critical factor influencing its success rate. The effectiveness is highest in the first 24 hours and decreases with each passing day. The manufacturer recommends taking it within 72 hours (3 days) of unprotected intercourse for maximum efficacy. While it can be used up to 120 hours (5 days), it is significantly less effective during this later period.
Studies show a range of effectiveness rates depending on when the pill is taken:
- Within 24 hours: Can be up to 94-95% effective at preventing pregnancy.
- Within 72 hours (3 days): Reduces the chance of pregnancy by 75-89%. Some studies suggest a lower effectiveness (around 58%) when taken between 48-72 hours.
- After 72 hours: The effectiveness continues to decrease and is considered less reliable.
Therefore, the definitive success rate for Afterpill is not a single number but a window of possibility directly tied to the speed of administration.
Factors That Influence Afterpill's Effectiveness
Beyond timing, several other factors can affect Afterpill's efficacy:
- Body Weight and BMI: Research indicates that levonorgestrel EC may be less effective for individuals weighing more than 165 pounds or with a BMI over 26 kg/m². For these individuals, a different EC option like Ella or a copper IUD may be more suitable.
- Stage of Menstrual Cycle: The pill works by delaying ovulation. If ovulation has already occurred, levonorgestrel is no longer an effective method of preventing pregnancy.
- Drug Interactions: Certain medications can interfere with the effectiveness of levonorgestrel. This includes some anti-seizure medications, St. John's Wort, and rifampin. It is crucial to consult a healthcare provider or pharmacist if you are taking other medications.
- Vomiting: If vomiting occurs within two hours of taking Afterpill, it may not have been fully absorbed. It is recommended to contact a healthcare professional to see if another dose is needed.
- Repeated Unprotected Sex: Afterpill provides no lasting protection. If you have unprotected sex again after taking the pill, you are not protected and would need another dose.
Comparison of Emergency Contraception Options
It's helpful to compare Afterpill to other available emergency contraception options to understand their relative effectiveness and suitability for different situations.
| Feature | Afterpill (Levonorgestrel) | Ella (Ulipristal Acetate) | Copper IUD |
|---|---|---|---|
| Effectiveness | 75-89% within 72 hours (decreases over time) | About 85% within 120 hours | >99% within 120 hours (most effective) |
| Timeframe | Up to 120 hours, but most effective within 72 | Up to 120 hours (5 days) | Up to 120 hours (5 days) |
| Body Weight | Potentially less effective over 165 lbs | Less effective over 195 lbs | No impact from body weight |
| Accessibility | Over-the-counter | Prescription required | Requires healthcare provider insertion |
| Primary Mechanism | Delays or prevents ovulation | Delays or prevents ovulation; blocks progesterone effects | Toxic to sperm and eggs, prevents implantation |
| Lasting Protection | None beyond current incident | None beyond current incident | Offers long-term contraception |
Important Considerations After Taking Afterpill
After taking Afterpill, you may experience some temporary side effects. These can include nausea, headaches, dizziness, fatigue, breast tenderness, and abdominal pain. It can also cause changes to your menstrual cycle, such as your next period being early, late, heavier, or lighter. If your period is more than a week late, you should take a pregnancy test to confirm whether the medication worked.
Emergency contraception is not intended for routine use. For ongoing contraception, talk to a healthcare provider about more effective, long-term options like birth control pills, patches, or IUDs. The morning-after pill also offers no protection against sexually transmitted diseases (STDs).
Conclusion
The success rate of Afterpill is not guaranteed and is highly dependent on when it is taken. For the best chance of preventing pregnancy, it must be taken as soon as possible, ideally within 24 hours of unprotected sex, and no later than 72 hours. Factors like body weight and drug interactions can also decrease its effectiveness. While a valuable backup option, it is not a substitute for regular contraception. For those seeking the highest efficacy in emergency contraception, the copper IUD is the most reliable option, irrespective of timing within the 5-day window or body weight. If you have any concerns, a conversation with a healthcare provider is recommended to discuss the most appropriate choice for your individual needs. For more details on emergency contraception, you can visit the Planned Parenthood website.
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional for guidance.
