Pharmacology · Selective oestrogen receptor modulators (SERMs)
Clomifene !
A tablet that tricks the brain into sensing low oestrogen, so it releases more hormones that make the ovary ovulate. Twins are more likely.
Updated 2026-11-01
Also called: clomiphene
The figure shows clomifene bound to the ligand-binding domain of human ERα.
Mechanism of action
Clomifene blocks oestrogen receptors in the hypothalamus. The hypothalamus reads this as low oestrogen and releases more GnRH, so the pituitary secretes more FSH and LH. The ovary then develops one or more follicles and ovulates. It only works when the hypothalamic-pituitary-ovarian axis is intact, as in polycystic ovary syndrome.
- Blocks oestrogen receptors in the hypothalamus
- Negative feedback is lost: more GnRH
- The pituitary releases more FSH and LH
- Follicles mature and ovulation occurs
Pharmacokinetics
- Absorption
- Taken by mouth
- Elimination
- Mainly in the faeces, with enterohepatic recycling
- Half-life
- Long; one of its two isomers can still be detected more than a month later
Indications
- Ovulation induction in women with ovulatory dysfunction who wish to become pregnant, including polycystic ovary syndrome Polycystic ovary syndrome →
Adverse effects
Common
- Hot flashes
- Abdominal or pelvic discomfort and bloating from ovarian enlargement
- Breast tenderness
- Nausea
- Headache
Contraindications
- Pregnancy
- Liver disease or history of liver dysfunction
- Abnormal uterine bleeding of unknown cause
- Ovarian cysts or enlargement not due to polycystic ovary syndrome
- Uncontrolled thyroid or adrenal disease
- Organic intracranial lesion such as a pituitary tumour
Key interactions
- Gonadotropins used in assisted reproduction
- Additive ovarian stimulation, with more risk of hyperstimulation and multiple pregnancy.
What is monitored
- Pregnancy test and pelvic examination before each course
- Ovulation tracking
- Ovarian size and symptoms of hyperstimulation
- Visual symptoms
Administration and safety
- Oral tablet for a few days per cycle, on the days set by the treating team.
- Courses are limited in number because benefit falls and risks rise with prolonged use.
Nursing care
- Confirm there is no pregnancy before each treatment course.
- Explain the higher chance of twins or more.
- Teach the warning signs of ovarian hyperstimulation: severe abdominal pain or swelling, rapid weight gain, shortness of breath, little urine.
- Teach the patient to stop and report blurred vision, spots or flashes; avoid driving while they last.
Pregnancy and breastfeeding
Contraindicated once pregnancy has occurred; it has no role during pregnancy.
Test yourself
Think of the answer, then tap the question to see it.
Why does blocking oestrogen receptors with clomifene lead to ovulation?
Blocking the receptors in the hypothalamus removes oestrogen's negative feedback; GnRH rises, the pituitary releases more FSH and LH, and the ovary develops and releases a follicle.
Which visual symptoms are a reason to stop clomifene and seek eye assessment?
Blurring, spots or flashes (scintillating scotomata); they are usually reversible but can persist.
Why does clomifene not work in women with pituitary failure?
It acts through the woman's own GnRH, FSH and LH; if the pituitary cannot respond, there is no rise in gonadotropins.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Clomiphene: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); DailyMed - CLOMIPHENE CITRATE tablet (DailyMed (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Estrogen Receptor Alpha Ligand Binding Domain in Complex with the Selective Estrogen Receptor Modulator Clomiphene (RCSB Protein Data Bank, 2020).
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Representative model, for educational purposes only.