Understanding Emergency Contraceptive Pills (ECPs)
Emergency contraceptive pills (ECPs), commonly known as morning-after pills, are a safe and effective way to prevent pregnancy after unprotected sex or contraceptive failure [1.2.4]. They are not the same as the abortion pill; ECPs work by preventing or delaying ovulation, so they do not interrupt an established pregnancy [1.5.1]. In the United States, there are two main types of morning-after pills available: pills containing ulipristal acetate and those containing levonorgestrel [1.5.1]. The most effective option depends on how much time has passed since intercourse, your body weight, and accessibility [1.8.2, 1.9.3]. The most effective form of emergency contraception overall is the copper IUD, which is over 99.9% effective and can be inserted up to five days after unprotected sex [1.2.4]. However, this article will focus on the pill options.
Ulipristal Acetate: The Most Effective Pill
Ulipristal acetate, sold under the brand name Ella, is the most effective emergency contraceptive pill available in the U.S. [1.2.2]. It is available by prescription only and can be taken up to 120 hours (five days) after unprotected sex [1.2.3, 1.5.1]. Studies have shown its effectiveness to be as high as 98% to 99.1% when taken within the five-day window [1.2.3, 1.2.4].
Ella's higher effectiveness is attributed to its mechanism of action. It works by delaying ovulation even after the luteinizing hormone (LH) surge has begun, which is a point when levonorgestrel pills are no longer effective [1.2.2]. This gives it a longer window of efficacy and makes it more reliable closer to ovulation [1.9.3].
Levonorgestrel: The Most Accessible Option
Levonorgestrel is the active ingredient in well-known brands like Plan B One-Step, as well as generic versions such as Take Action, My Way, Aftera, and EContra [1.5.1]. These pills are available over-the-counter without a prescription or age restriction [1.5.1].
Levonorgestrel pills are most effective when taken within 72 hours (three days) of unprotected sex, though they can be taken up to five days after with reduced efficacy [1.5.1]. The sooner they are taken, the better they work, with studies showing effectiveness can be around 94% if taken in the first 24 hours [1.2.3, 1.9.5]. The primary mechanism of action is delaying or inhibiting ovulation [1.4.2].
Key Factors That Influence Effectiveness
Choosing the most effective brand for your situation requires considering several variables:
Timing: This is the most critical factor [1.8.3].
- Ulipristal acetate (Ella): Maintains high effectiveness for up to 120 hours (5 days) [1.2.3].
- Levonorgestrel (Plan B, etc.): Works best within 72 hours (3 days), and its effectiveness decreases significantly after that [1.5.1].
Body Weight and BMI: Research indicates that body weight can impact the efficacy of morning-after pills [1.3.6].
- Levonorgestrel (Plan B, etc.): May be less effective in individuals who weigh over 165 pounds or have a BMI over 25 [1.3.1, 1.8.2].
- Ulipristal acetate (Ella): Is considered more effective for individuals who weigh between 165 and 195 pounds [1.3.2]. Its effectiveness may decrease for those over 195 pounds [1.3.5].
- The copper IUD's effectiveness is not affected by weight [1.3.5].
Drug Interactions: Certain medications can make ECPs less effective. These include the herbal supplement St. John's Wort and some drugs used to treat seizures, tuberculosis, and HIV [1.8.3, 1.9.4].
Comparison Table: Ella vs. Levonorgestrel
| Feature | Ella (Ulipristal Acetate) | Plan B & Generics (Levonorgestrel) |
|---|---|---|
| Active Ingredient | 30 mg Ulipristal Acetate [1.2.4] | 1.5 mg Levonorgestrel [1.2.4] |
| Effectiveness Window | Up to 120 hours (5 days) [1.5.1] | Most effective within 72 hours (3 days) [1.5.1] |
| Prescription Needed? | Yes [1.5.1] | No, available over-the-counter [1.5.1] |
| Effectiveness Rate | 97.9% to 99.1% [1.2.4] | Reduces pregnancy risk by 81-90% within 72 hours [1.2.1] |
| Impact of Weight | More effective up to 195 lbs [1.3.1] | Less effective over 165 lbs [1.3.1] |
| Cost (Out-of-Pocket) | ~$40 - $68 [1.6.4] | ~$11 - $53 (Generics are cheaper) [1.6.2] |
Side Effects, Cost, and Availability
Common side effects for both types of pills are generally mild and can include nausea, headache, changes in your next period (it may be earlier, later, or heavier), abdominal pain, and breast tenderness [1.4.1, 1.4.5, 1.8.1]. If you vomit within two to three hours of taking a pill, you should contact a healthcare provider to see if you need another dose [1.8.3].
Cost and Availability: Levonorgestrel pills like Plan B and its generics are widely available at drugstores and pharmacies and are generally cheaper, with prices ranging from $11 to over $50 [1.5.1, 1.6.2]. Ella requires a prescription from a doctor or a telehealth service and typically costs between $40 and $68 out-of-pocket, though it may be covered by insurance [1.6.4, 1.6.2].
Conclusion: Which Brand Is Best?
Based on clinical effectiveness alone, Ella (ulipristal acetate) is the most effective morning-after pill brand [1.2.2]. It has a longer window of use and is more effective than levonorgestrel, especially when taken closer to ovulation or for individuals with a higher body weight [1.2.2, 1.3.4].
However, levonorgestrel pills (like Plan B and its generics) are the best option when accessibility is the primary concern. Their over-the-counter availability makes them a crucial and time-sensitive choice for many [1.5.1]. The most important rule is that taking any ECP as soon as possible after unprotected sex is better than taking nothing at all [1.8.2]. For long-term and highly effective emergency and ongoing contraception, the copper IUD is the superior choice [1.2.4].
For more information, you can consult with a healthcare provider or visit Planned Parenthood.
