Progesterone
progestins
Progestogens (progestins)Pregnancy: contraindicated
The oral capsule is not used during pregnancy, according to its label.
The natural ovarian hormone, as oral capsules, used with estrogen to protect the uterus after menopause and to bring on a period in amenorrhoea.
Also called: Micronised progesterone
Quick facts
- Group
- Progestogens (progestins)
- Target
- Progesterone receptor (PR), a nuclear receptor
- Used for
- Prevention of endometrial hyperplasia
- Key effects
- Drowsiness and dizziness · Headache · Abdominal pain
- Monitor
- Abnormal vaginal bleeding · Blood pressure
- ATC
- G03DA04
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows progesterone itself in the ligand-binding domain of the human progesterone receptor.
Therapeutic progesterone is chemically identical to the hormone of the corpus luteum. It activates the progesterone receptor in the endometrium, which changes the estrogen-primed lining from proliferative to secretory and limits its growth. Given for part of each cycle alongside estrogen, it prevents endometrial hyperplasia; stopping it after a course causes a withdrawal bleed in secondary amenorrhoea.
- Progesterone binds the progesterone receptor of the endometrium
- The estrogen-primed lining becomes secretory
- Endometrial growth is limited, preventing hyperplasia
- Stopping it after a course triggers a withdrawal bleed
Indications
- Prevention of endometrial hyperplasia in postmenopausal women with a uterus taking estrogen Endometrial hyperplasia →
- Part of menopausal hormone therapy with estrogen Menopause and climacteric syndrome →
- Secondary amenorrhoea
Adverse effects
Common
- Drowsiness and dizziness
- Headache
- Breast tenderness
- Abdominal pain, bloating
- Mood changes, fatigue
Contraindications
- Allergy to peanuts (the capsules contain peanut oil) or other ingredients
- Undiagnosed abnormal genital bleeding
- Known, suspected or past breast cancer
- Active or past venous thromboembolism, stroke or heart attack
- Liver disease
- Pregnancy, known or suspected
Key interactions
- Ketoconazole and other CYP3A4 inhibitors
- Higher progesterone levels
- St John's wort
- May lower progesterone levels
What is monitored
- Abnormal vaginal bleeding
- Blood pressure
- Breast examination and mammography as for any menopausal therapy
- Signs of thrombosis or visual change
- Drowsiness
Administration and safety
- Oral capsule taken at bedtime, because it causes drowsiness and dizziness
- Taken on the cycle days the regimen sets, with estrogen
- With difficulty swallowing, taken with a full glass of water while standing
- Peanut allergy is asked about before the first dose
Pregnancy and breastfeeding
The oral capsule is not used during pregnancy, according to its label.
Nursing care
- Ask about peanut allergy before giving it
- Teach to take it at bedtime and to take care driving or using machines
- Teach to rise slowly to avoid fainting
- Teach warning signs: leg pain or swelling, chest pain, sudden breathlessness, weakness, vision change, breast lump
- Report any unexpected vaginal bleeding
Pharmacokinetics
- Absorption
- Oral capsules; food increases absorption
- Distribution
- Very highly protein-bound
- Metabolism
- Mainly in the liver to pregnanediols and pregnanolones; CYP3A4 inhibitors raise its levels
- Elimination
- Conjugated metabolites, mostly in urine
- Onset and duration
- Peak levels within a few hours of a dose
Test yourself
Think of the answer, then tap the question to see it.
Why are progesterone capsules taken at bedtime?
They can cause marked drowsiness and dizziness.
Which food allergy contraindicates oral progesterone capsules?
Peanut allergy: the capsules contain peanut oil.
What is the main purpose of progesterone in menopausal hormone therapy?
To protect the endometrium of a woman with a uterus from estrogen-driven hyperplasia.
Connections
← Back to the class: Progestogens (progestins)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - PROGESTERONE capsule (DailyMed (U.S. National Library of Medicine), 2026); Progesterone: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.