Levonorgestrel

Category: hormone

Aliases: Plan B, Mirena IUD

Pharmacological Mechanism

Synthetic progestin — strong progestational + weak androgenic activity. Backbone of combined oral contraceptives, the LNG-IUD (Mirena), and emergency contraception (Plan B One-Step) where high-dose interferes with ovulation timing. CYP3A4 substrate (induction lowers efficacy).

Half-Life (t½)

PO: 11.55h

Dosing Guidelines

Target Organ Systems