Definitions

Emergency contraception (EC): Use of an intervention shortly after coitus to prevent pregnancy. Yuzpe regimen: Use of a specific oral contraceptive regimen first reported by Dr. Yuzpe. consisting of two tablets of Ovral oral contraceptives (total of 0.1 mg ethinyl estradiol and 0.5 mg levonorgestrel) at time zero and two tablets after 12 hr. Plan B (progestin only): Levonorgestrel 0.75 mg taken orally at time zero and the same dose after 12 hr.

Clinical Approach

EC is the therapy for women who have had unprotected sexual intercourse, including victims of sexual assault. It is also known as the "morning after pill." The two most common regimens are the combination oral contraceptive method, known as the Yuzpe method, and the progestin-only regimen. The Yuzpe method consists of 0.1 mg ethinyl estradiol and 0.5 mg levonorgestrel in two doses, 12 hr apart, beginning within 72 hr of unprotected intercourse. Because some studies suggest that EC may be effective within 120 hr after unprotected intercourse, it may be offered within this window. The progestin-only (plan B) method consists of 0.75 mg levonorgestrel in two doses taken 12 hr apart. The mechanisms of action may include inhibition of ovulation, decreased tubal motility, and, possibly, interruption of implantation.

The efficacy of the combination method is accepted to be an approximately 75% reduction in pregnancy rate, thus decreasing the risk of a mid-cycle coital pregnancy from 8: KM) to approximately 2:100. The progestin-only method appears to have slightly greater efficacy, with a pregnancy risk reduction of approximately 85%.

The major side effect of EC is nausea and/or tmesis, which is more prominent with the combination method. An antiemetic often is prescribed with the Yuzpe regimen. EC should not be used in patients with a suspected or known pregnancy or in those with abnormal vaginal bleeding. Women who do not have onset on menses within 21 days following EC should have a pregnancy test.

Comprehension Questions

[34.11 Which of the following describes the mechanism(s) whereby combination oral contraceptive therapy may act in emergency contraception?

A. Inhibition of ovulation

B. Decrease in tubal motility

C. Inhibition of implantation

D. AH the of the above

[34.21 Which of the following is the most common side effect of the Yuzpe regimen?

A. Vaginal spotting

B. Nausea and/or vomiting

C. Elevation of liver function enzymes

D. Glucose intolerance

E. Renal insufficiency

[34.31 Which of the following is the main effect of the progestin-only regimen compared with the Yu/pe regimen in emergency contraception?

A. Higher ectopic pregnancy rate

B. Less effective prevention of pregnancy

C. Less nausea

D. More liver dysfunction

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