PROMETRIUM (progesterone) FDA Label - Drug Interactions (DailyMed)

Tier 1: Established: peer-reviewed research or government health authority
Publisher: U.S. National Library of Medicine / DailyMed (FDA-approved labeling) · Published: September 16, 2026 · Accessed: September 16, 2026

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Claims this source supports

• Progesterone is metabolized by human liver microsomes; that metabolism was inhibited by ketoconazole (IC50 < 0.1 micromolar).
• Ketoconazole is a known inhibitor of cytochrome P450 3A4, so the label states that ketoconazole or other known inhibitors of this enzyme may increase the bioavailability of progesterone.
• The label notes the clinical relevance of the in vitro findings is unknown.