How Plan B Works to Prevent Pregnancy
To understand potential interactions, it's crucial to know how emergency contraception like Plan B One-Step functions. The active ingredient in Plan B is levonorgestrel, a synthetic hormone similar to progesterone. Plan B works primarily by temporarily delaying or preventing ovulation—the release of an egg from the ovary. By postponing ovulation, the medication ensures there is no egg available for a sperm to fertilize. The manufacturer and the U.S. Food and Drug Administration (FDA) have also confirmed that Plan B will not work if a woman is already pregnant and cannot terminate an existing pregnancy. It is a form of emergency contraception, not an abortion pill. Its effectiveness is highest when taken as soon as possible after unprotected sex, ideally within 72 hours.
The Myth of Vitamins and Plan B
The notion that certain foods or supplements, particularly vitamins, can render Plan B ineffective is a common misconception. Several comprehensive drug interaction databases, such as Drugs.com, show no known interactions between Plan B and standard vitamins like Vitamin C, Vitamin B12, or multivitamins. The safety of combining these is well-established. For instance, a study published in Contraception found that high oral doses of Vitamin C did not affect the bioavailability of levonorgestrel in women. While some long-term hormonal contraceptive methods might affect certain nutrient levels over time, this is not the case for a single-dose emergency contraceptive like Plan B.
Therefore, taking a daily multivitamin or specific vitamin supplements will not decrease the effectiveness of Plan B. You can take your vitamins as usual without concern when you need to use emergency contraception.
Vitamins and supplements that do NOT cancel out Plan B
- Multivitamins: No known interaction.
- Vitamin C: No known interaction, even at high doses.
- Vitamin B12: No known interaction.
- Vitamin D: No known interaction.
- Probiotics: Safe to take, no interference with hormones.
- Magnesium and Zinc: No interference with Plan B's effectiveness.
Real Threats to Plan B's Effectiveness
While vitamins are safe, it is crucial to be aware of other substances that can reduce Plan B's effectiveness. These substances can speed up the metabolism of the levonorgestrel hormone in your body, meaning it is cleared from your system faster and has less time to work effectively.
Substances that can reduce Plan B's effectiveness:
- Herbal Supplements: St. John's wort, a herbal supplement often used for depression, is a known inhibitor of Plan B's efficacy.
- HIV/AIDS Medications: Certain antiviral medications, including efavirenz, can interfere with Plan B.
- Tuberculosis Treatment: The antibiotic rifampin is known to make Plan B less effective.
- Certain Seizure Medications: A number of antiepileptic drugs, such as carbamazepine, phenytoin, and topiramate, can decrease the level of levonorgestrel in the body.
- Activated Charcoal: This substance can absorb the medication in the digestive tract, preventing it from being absorbed into your system.
What to Do If You've Taken an Interacting Substance
If you have taken any of the medications or herbal supplements listed above, it is important to consult a healthcare provider. They can advise you on the best course of action. In some cases, a different form of emergency contraception, such as the copper IUD, may be a more reliable option. The copper IUD can be inserted up to five days after unprotected sex and is the most effective form of emergency contraception available.
Comparison of Factors Affecting Plan B's Effectiveness
| Factor | Impact on Plan B's Effectiveness | How It Works | What You Should Do |
|---|---|---|---|
| Vitamins (e.g., C, Multi) | No Impact | They do not interfere with how levonorgestrel is absorbed or metabolized by the body. | No change needed; continue with your vitamin regimen. |
| St. John's Wort | Decreased | This herbal supplement can speed up the metabolism of the Plan B hormone. | Avoid using this supplement and consult a healthcare provider for alternative emergency contraception options if needed. |
| Timing of Use | Decreased over time | The sooner Plan B is taken after unprotected sex, the more effective it is. | Take Plan B as soon as possible after unprotected sex for the best results. |
| Body Weight | Decreased in higher BMI | Some research suggests levonorgestrel-based pills are less effective for people with a higher body mass index (BMI). | Consult a healthcare provider, who may recommend a different option like the copper IUD or ella. |
| Certain Medications (e.g., Carbamazepine) | Decreased | These drugs speed up the liver enzymes that break down levonorgestrel. | Speak with a healthcare professional to determine if a non-interacting contraceptive is necessary. |
Conclusion
It is a relief to know that common vitamins and multivitamin supplements do not interfere with the effectiveness of Plan B. The primary factors that influence Plan B's efficacy are the timing of its use and interactions with certain medications and herbal supplements like St. John's wort. Always take Plan B as soon as possible for the best results. If you are taking any medications, including those for seizures or HIV, it is important to consult a healthcare professional or pharmacist to ensure your emergency contraception will work as intended. Always prioritize reliable contraception and seek advice from a medical expert when in doubt. For additional information on contraception, you can visit the Planned Parenthood website. Planned Parenthood
