Dose of levonorgestrol for contraception is
**Core Concept**
The question is testing the understanding of the pharmacological principle behind emergency contraception using levonorgestrel, a synthetic progestin. Levonorgestrel works by inhibiting or delaying ovulation, thereby preventing fertilization.
**Why the Correct Answer is Right**
The recommended dose of levonorgestrel for emergency contraception is 1.5 mg, taken as a single dose within 72 hours of unprotected sex. This dose is effective in preventing ovulation by suppressing the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn reduces the secretion of luteinizing hormone (LH) from the pituitary gland. The inhibition of LH surge prevents the rupture of the follicle and the release of an ovum.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the dose of levonorgestrel for emergency contraception is not 0.5 mg. A lower dose may not be effective in preventing ovulation.
**Option B:** This option is incorrect because the dose of levonorgestrel for emergency contraception is not 2 mg. A higher dose may increase the risk of side effects without providing additional benefit.
**Option D:** This option is incorrect because the dose of levonorgestrel for emergency contraception is not 3 mg. A higher dose may increase the risk of side effects without providing additional benefit.
**Clinical Pearl / High-Yield Fact**
It's essential to note that levonorgestrel emergency contraception is most effective when taken as soon as possible after unprotected sex, with a reported efficacy rate of up to 95% when taken within 24 hours.
**Correct Answer: C. 1.5 mg**