Levonorgestrel

Levonorgestrel is a synthetically derived progestin used primarily in emergency contraception and standard oral contraceptives. It acts as an agonist of the progesterone receptor, providing effective contraception by preventing ovulation.

Levonorgestrel

Pharmacological Profile

Levonorgestrel operates as an emergency contraceptive by hindering the luteinizing hormone (LH) surge that precedes ovulation. Its efficiency is observed predominantly when administered before this LH surge, and it demonstrates minimal effects on fertilization or implantation.

Clinical Efficacy

Clinical studies have evidenced the efficacy of levonorgestrel in significantly lowering the rate of unwanted pregnancies when used within 48 hours of unprotected intercourse or suspected contraceptive failure. The overall failure rates range from 0.6% to 3.1%, compared to expected rates of 5% to 6%.

Approval and Usage

The United States Food and Drug Administration (FDA) approved levonorgestrel for emergency contraception use in 1982. Available generically and over-the-counter, it is administered in tablet form in doses of 0.75 and 1.5 mg. The recommended regimen for emergency contraception is a total dose of 1.5 mg, taken within 72 hours of unprotected intercourse or suspected contraceptive failure.

Levonorgestrel also serves as a constituent of standard oral contraceptives, where it is used alone or in combination with estrogens.

Safety Profile

The use of levonorgestrel has not been associated with liver enzyme elevations or clinically apparent liver injury with jaundice.

Adverse Effects

Potential side effects of levonorgestrel use, generally mild-to-moderate in severity, can include headache, nausea, abdominal pain, dysmenorrhea, breast tenderness, fatigue, and dizziness.

Obstetrical and Gynecological Agents

• Emergency contraceptive agents
  • Levonorgestrel, Ulipristal

• Estrogens and Oral contraceptives

• • Selective estrogen receptor modulators
    • Bazedoxifene, Ospemifene, Raloxifene
  • Infertility agents

• Antiestrogens
  • Clomiphene, Letrozole, Tamoxifen

• Gonadotropins
  • Chorionic gonadotropin, Follicle stimulating hormone, Luteinizing hormone, Human gonadotropin releasing hormone

• Pregnancy termination agents
  • Mifepristone
• Progesterone and the Progestins

• Dailymed label info on Levonorgestrel
• FDA Levonorgestrel

Levonorgestrel Resources
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