Levonorgestrel (Plan B) for women who do not desire pregnancy:

• A. Is prescription only
• B. Should be taken within 7 days of unprotected sex
• C. Is 99% effective against pregnancy
• D. Inhibits fertilization or implantation of the fertilized egg

Answer: (D)

Levonorgestrel, commonly known as Plan B, is a progestin used for emergency contraception. Its primary mechanism of action is to prevent or delay ovulation, which reduces the chance of fertilization. If fertilization has already occurred, it may also alter the endometrial lining to inhibit implantation of a fertilized egg. This is why the option regarding its role in inhibiting fertilization or implantation is accurate.

The time frame for taking the medication is crucial; it is most effective when taken as soon as possible after unprotected sex, ideally within 72 hours, but it can be taken up to 5 days after. Although it is effective in preventing pregnancy, it is not 99% effective; its effectiveness can range from 75% to 89% depending on how soon it is taken after intercourse. Additionally, while Plan B was available over-the-counter in most regions, understanding the accessibility of levonorgestrel can vary, so it is essential for healthcare providers to stay informed about the current status of this medication's availability.