Plan B (levonorgestrel emergency contraception) is a medication designed to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. It serves as a backup method, not a routine form of birth control. Plan B works primarily by delaying or preventing ovulation, the release of an egg from the ovary.
Alcohol’s Impact on Plan B
Consuming alcohol does not reduce the effectiveness of Plan B. The active ingredient, levonorgestrel, is metabolized separately from alcohol, with no known interaction affecting its absorption or mechanism of action. Official prescribing information for Plan B does not list alcohol as a substance that alters its efficacy.
While alcohol itself does not impact Plan B, excessive consumption can lead to impaired judgment, potentially increasing the risk of unprotected sexual encounters. Both alcohol and Plan B can cause side effects such as nausea, vomiting, dizziness, and headache. Combining them might intensify these temporary symptoms, but this does not mean Plan B is less effective at preventing pregnancy.
Why People Might Link Alcohol and Plan B
Misconceptions about alcohol affecting Plan B often stem from general warnings about mixing alcohol with various medications. Many medications, including some antibiotics, antidepressants, and pain relievers, can interact with alcohol, potentially leading to increased side effects or reduced drug effectiveness. This general cautionary advice can lead individuals to assume that alcohol interferes with all medications, including emergency contraception.
Anxiety surrounding the effectiveness of emergency contraception also plays a role in these concerns. Individuals often seek to maximize Plan B’s chances of success, leading them to question any potential inhibitors. The overlapping side effects of alcohol and Plan B, such as nausea or dizziness, might be mistakenly interpreted as a negative drug interaction rather than simply additive symptoms.
What Truly Affects Plan B’s Effectiveness
Several factors can genuinely influence how well Plan B works. Timing is one of the most significant; Plan B is most effective when taken as soon as possible after unprotected sex. While it can be taken up to 72 hours (three days) after the event, some formulations may be effective for up to 120 hours (five days), though efficacy generally decreases with each passing hour.
Body mass index (BMI) or weight can also impact Plan B’s efficacy. Studies suggest that levonorgestrel-based emergency contraception may be less effective for individuals weighing more than approximately 155 to 165 pounds or with a BMI above 25 or 30. For those in higher weight ranges, alternative emergency contraception options like ulipristal acetate (Ella) or a copper intrauterine device (IUD) are often more effective.
Vomiting soon after taking Plan B can also compromise its effectiveness. If vomiting occurs within two to three hours of taking the pill, the medication may not have been fully absorbed. In such cases, it is advisable to consult a healthcare professional, as another dose might be necessary to ensure adequate absorption.
Certain medications can interfere with Plan B’s action by accelerating the metabolism of levonorgestrel, thereby reducing its concentration. These include:
- Specific anti-seizure medications (e.g., carbamazepine, phenytoin, topiramate)
- The herbal supplement St. John’s Wort
- Some HIV medications
- The antibiotic rifampin
Individuals taking other medications should discuss potential interactions with a pharmacist or doctor to determine the best emergency contraception option.