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

• PO: Typical 0.15 mg (Range: 0.03–1.5 mg)

Target Organ Systems

• digestive
• reproductive

Pathways It Modulates

• Hypothalamic-pituitary-gonadal axis (activator) — PR (progestin) + weak AR
• Progesterone receptor signaling (activator) — PR (synthetic progestin; LNG-IUD, EC, OC)

Chemical Identifiers

• PubChem CID: 13109
• Formula: C21H28O2
• Molecular weight: 312.45 g/mol
• InChIKey: WWYNJERNGUHSAO-XUDSTZEESA-N
• SMILES: CC[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@]2(C#C)O)CCC4=CC(=O)CC[C@H]34

References

• PMID 6786829