Plan B^® is composed of progestin-only (levonorgestrel) tablets. Levonorgestrel is well-trusted and has been commonly used in many birth control pills for over 35 years. Plan B^® also has a superior tolerability profile compared to the Yuzpe regimen (levonorgestrel and ethinyl estradiol); in a clinical trial, 23% of women taking Plan B^® experienced nausea and 5.6% experienced vomiting.

Plan B^® is safe and well tolerated. Some women may experience mild side effects, similar to those of regular birth control pills. The most common include: nausea, abdominal pain, fatigue, headache, menstrual changes, dizziness, breast tenderness, vomiting, and diarrhea. After taking Plan B^®, they should be informed that their next period may be heavier or lighter, earlier or later. In a clinical trial, the majority of women (87%) had their menstrual period at the expected time or within ±7 days. Patients should be advised that if their period is more than one week late, they may be pregnant. If your patient experiences severe abdominal pain, she may have an ectopic pregnancy and should seek immediate medical attention.