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Hormone replacement / oestrogen Pregnancy: SPC 4.6: Pregnancy - 'This medicine is not indicated during pregnancy.' For women with a uterus: if pregnancy occurs during treatment it should be withdrawn immediately; the results of most epidemiological studies relevant to inadvertent foetal exposure to oestrogens indicate no teratogenic or foetotoxic effects. Breast-feeding - 'This medicine is not indicated during lactation.'

Conjugated oestrogens

Brand names: Premarin

Conjugated oestrogens are a preparation of oestrogenic compounds used in hormone replacement therapy for menopausal symptoms and oestrogen deficiency.

Adult dose

Dose: Oestrogen-only hormone replacement therapy for oestrogen deficiency symptoms in postmenopausal women (conjugated oestrogens 0.625 mg coated tablets, Premarin): 0.3-1.25 mg daily is the usual starting dose for women without a uterus; continuous administration is recommended. To control menopausal symptoms, initiate treatment with 0.3 mg of conjugated oestrogens; if symptoms are not adequately controlled, higher doses may be prescribed; once treatment is established use the lowest effective dose necessary for relief of symptoms
Route: Oral
Frequency: Daily, continuous administration
SOURCE: UK SPC for ONE product - conjugated oestrogens 0.625 mg coated tablets / Premarin 0.625 mg coated tablets (PL000571285, Pfizer Limited); each tablet contains 0.625 mg conjugated oestrogens (plus lactose monohydrate 54.1 mg and sucrose 45 mg). This SPC does not state which tablet strength supplies the 0.3 mg initiation dose, and 4.2 says tablets 'should be taken whole; do not divide, crush, chew, or dissolve tablets in mouth'. The SPC prints no maximum dose, so none is given. INDICATIONS (4.1): HRT for oestrogen deficiency symptoms in postmenopausal women; and prevention of osteoporosis in postmenopausal women at high risk of future fractures who are intolerant of, or contraindicated for, other medicinal products approved for the prevention of osteoporosis. 4.2 prints no separate dose for the osteoporosis indication. SCOPE - ORAL TABLETS ONLY: this page also lists a topical (vaginal) route; this SPC does not cover vaginal conjugated oestrogens, so no vaginal dose is given and that product's regimen differs. WOMEN WITH A UTERUS: this medicine is an oestrogen-only HRT; where a progestogen is necessary it 'should be added for at least 12-14 days every 28 day cycle to reduce the risk to the endometrium'; unless there is a previous diagnosis of endometriosis it is not recommended to add a progestogen in hysterectomised women (4.2). 4.4: 'For oral doses of conjugated equine oestrogens >0.625 mg the endometrial safety of added progestogens has not been demonstrated.' START/CHANGE: in women not taking HRT or switching from a continuous combined HRT product, start on any convenient day; from a sequential regimen, begin the day after completing the prior regimen. MISSED TABLET: take it as soon as remembered and continue as before; if more than one is forgotten take only the most recent, never a double dose; missed tablets may cause breakthrough bleeding in women with a uterus. ELDERLY: 'no special dosage requirements', lowest effective dose. CHILDREN: safety and effectiveness in paediatric patients have not been established, so no paediatric dose is given; hormonal therapy should not be started before epiphyseal closure. Some sections of the product information we used were incomplete — check the full SPC.

Dose adjustments

Renal

No renal-impairment dosing advice is printed in section 4.2 of this SPC.

Hepatic

No hepatic dose adjustment is printed in section 4.2; contraindicated in acute liver disease or a history of liver disease where liver function tests have failed to return to normal (4.3).

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Known, suspected or history of breast cancer
  • Known or suspected oestrogen-dependent malignant tumours (e.g. endometrial cancer)
  • Undiagnosed genital bleeding
  • Untreated endometrial hyperplasia
  • Previous or current venous thromboembolism (e.g. deep vein thrombosis, pulmonary embolism)
  • Known thrombophilic disorders (e.g. protein C, protein S or antithrombin deficiency)
  • Active or recent arterial thromboembolic disease (e.g. angina, myocardial infarction)
  • Acute liver disease, or history of liver disease where liver function tests have failed to return to normal
  • Hypersensitivity to the active substance or to any of the excipients listed in section 6.1
  • Porphyria

Side effects

  • Vaginitis, including vaginal candidiasis
  • Fibrocystic breast changes; ovarian cancer; growth potentiation of benign meningioma; enlargement of hepatic haemangiomas
  • Hypersensitivity; anaphylactic/anaphylactoid reactions, including urticaria and angioedema
  • Glucose intolerance; exacerbation of porphyria; hypocalcaemia
  • Depression; changes in libido; mood disturbances; irritability
  • Dizziness, headache, migraine, anxiety; stroke; exacerbation of epilepsy; exacerbation of chorea
  • Intolerance to contact lenses; retinal vascular thrombosis
  • Myocardial infarction; venous thrombosis; pulmonary embolism; superficial thrombophlebitis
  • Exacerbation of asthma
  • Nausea, bloating, abdominal pain; vomiting; pancreatitis; ischaemic colitis
  • Gallbladder disease; cholestatic jaundice
  • Alopecia; chloasma/melasma; hirsutism; pruritus; rash
  • Arthralgias; leg cramps
  • Abnormal uterine bleeding (breakthrough bleeding/spotting); breast pain, tenderness, enlargement, discharge; leucorrhoea; change in menstrual flow; change in cervical ectropion and secretion; dysmenorrhoea/pelvic pain; galactorrhoea; increased size of uterine leiomyomata
  • Oedema; changes in weight (increase or decrease); increased triglycerides; increases in blood pressure
  • Breast cancer: an up to 2-fold increased risk is reported in women taking combined oestrogen-progestogen therapy for more than 5 years; the increased risk in users of oestrogen-only therapy is lower; the level of risk depends on duration of use (4.8)

Interactions

  • CYP3A4 inducers (St John's wort, phenobarbital, phenytoin, carbamazepine, rifampicin, rifabutin, nevirapine, efavirenz, dexamethasone) may reduce plasma oestrogen concentrations, possibly decreasing therapeutic effect and/or changing the uterine bleeding profile
  • CYP3A4 inhibitors (cimetidine, erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir, nelfinavir, grapefruit juice) may increase plasma oestrogen concentrations and may result in side effects
  • Lamotrigine: oestrogen-containing hormone contraceptives significantly decrease plasma lamotrigine concentrations; a similar interaction is expected with HRT, which may reduce seizure control
  • Laboratory test interference: oestrogens increase thyroid-binding globulin, corticosteroid-binding globulin and sex hormone-binding globulin, increase platelet count, reduce antithrombin III, impair glucose tolerance and may reduce the response to metyrapone

Monitoring

  • Before starting or restarting HRT take a complete personal and family medical history and perform a physical (including pelvic and breast) examination guided by it
  • Periodic check-ups during treatment; mammography and other investigations in line with accepted screening practice
  • Careful appraisal of risks and benefits at least annually; continue HRT only as long as the benefit outweighs the risk
  • Re-evaluate periodically to determine whether treatment for symptoms is still necessary
  • Breakthrough bleeding or spotting that appears after some time on therapy, or continues after stopping, should be investigated (may include endometrial biopsy)
  • Discontinue if jaundice or deterioration in liver function, significant increase in blood pressure, new-onset migraine-type headache, or pregnancy occurs

Clinical monograph

How it works

They bind oestrogen receptors to replace declining endogenous oestrogen, relieving vasomotor and urogenital symptoms of oestrogen deficiency.

Prescribing in practice

  • In women with an intact uterus, oestrogen must be combined with a progestogen to oppose endometrial proliferation and reduce the risk of endometrial hyperplasia and carcinoma.
  • Hormone replacement therapy is associated with increased risks of venous thromboembolism, stroke, and certain cancers that vary with age and regimen, and treatment should be reviewed regularly at the lowest effective dose.
  • It is contraindicated in oestrogen-dependent cancers, undiagnosed vaginal bleeding, active thromboembolic disease, and active liver disease.

Monitoring

Review symptoms, blood pressure, breast awareness, and any abnormal bleeding periodically, and reassess the benefit-risk balance of continuing therapy.

Counselling the patient

  • Report any unexpected or unscheduled vaginal bleeding.
  • Seek urgent advice for symptoms of a clot, such as leg swelling, chest pain, or sudden breathlessness.
  • Attend routine breast screening and report any new breast changes.

Evidence & guidelines

NICE menopause guidance supports hormone replacement therapy for menopausal symptoms with an individualised discussion of its benefits and risks.

Reference: NICE NG23; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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