Generic Name

emergency contraceptive

Mechanism

• Primary action: Delays or inhibits ovulation by suppressing the LH surge.
• Secondary actions:
• Alters endometrial lining, reducing implantation potential.
• Slows cervical mucus movement, limiting sperm motility.

The compound acts most effectively when administered before the LH surge occurs; its efficacy diminishes as the cycle progresses toward ovulation.

Pharmacokinetics

Indications

• Emergency contraception after a single episode of unprotected intercourse or contraceptive failure.
• Administered ≤72 h after intercourse (optimal <24 h).
• Suitable for women of reproductive age who desire temporary contraception.

Contraindications

• Contraindications
• Known hypersensitivity to levonorgestrel or any formulation excipient.
• Current use of anticoagulants (e.g., warfarin) – may increase clotting risk.
• Warnings
• Pregnancy: Not indicated for use after implantation or in confirmed pregnancies.
• Thromboembolic risk: Slightly elevated in women with clotting disorders; consider individual risk.
• Multiple dose use: Repeated use should be spaced ≥21 days; avoid within 48 h of another dose.
• Precautions
• Should not be used as a regular contraceptive; does not offer protection during the cycle.

Dosing

• Standard dose: 1 tablet containing 1.5 mg levonorgestrel.
• Timing:
• Ideally within 24 h for optimal efficacy (~90 %).
• Acceptable up to 72 h (efficacy ~63 %).
• Administration: Oral; can be taken with or without food.
• If taken >72 h: Consider alternative emergency contraception (ulipristal acetate, copper IUD).

Adverse Effects

Monitoring

• Post‑dose follow-up: Reassure patient; offer pregnancy test if menstruation is significantly delayed.
• VTE risk assessment before administration in high‑risk populations (smoking, obesity, personal/family clotting history).
• Reproductive health counseling: Discuss long‑term contraception options and potential menstrual irregularities.

Clinical Pearls

• Timing is king: Each hour of delay after intercourse reduces efficacy, especially beyond 48 h.
• Metabolic interactions: CYP3A4 inducers (e.g., rifampin, carbamazepine) lower levonorgestrel levels; consider a second dose within 24 h if exposure to inducers is ongoing.
• Absorption concern: Vomiting within 3 h of ingestion may necessitate repeat dose; otherwise, efficacy remains largely intact.
• Patient counseling: Emphasize that Plan B is not a provider for ongoing contraception and that regular birth‑control methods should be discussed afterwards.
• Safety in pregnancy: If a woman inadvertently takes Plan B while pregnant, no evidence suggests teratogenic risk; but the medication will have little effect and should not be considered therapeutic.
• Educational tip: Distinguish Plan B from ulipristal acetate (Ella) – the former is progestin‑only, the latter a selective progesterone receptor modulator with longer window (~5 days).

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• Key takeaways: Plan B (levonorgestrel) is a *rapid, reliable, and widely accessible emergency contraceptive* when taken within 72 h of unprotected sex, with a favorable safety profile in healthy women. Precise timing, patient selection, and proper counseling maximize its clinical utility.