Premarin

Basic Premarin information

• INN (international nonproprietary name): Conjugated oestrogens.
• Brand names available in the United Kingdom: Premarin (marketed by Pfizer; pack sizes and strengths for the UK include 0.3 mg, 0.625 mg and 1.25 mg tablets in boxes of 28)
• ATC code: G03CA57.
• Forms and dosages: tablets 0.3 mg, 0.625 mg and 1.25 mg.
• Manufacturers in the United Kingdom: Pfizer.
• Registration status in the United Kingdom: Registered; prescription-only medicine (POM).
• OTC / Rx classification: Prescription-only medicine (POM)

Legal status and availability in the UK

Premarin is a prescription-only medicine (POM) in the UK.

In our online pharmacy, Premarin is available without a prescription, with discreet delivery to the United Kingdom in 9–21 days.

Product identity, composition and classification

Active substance and pharmacological class

What is in Premarin and how is it classified?

The INN for Premarin is conjugated oestrogens, a mixture of natural oestrogens derived from equine sources.

The ATC code is G03CA57, classifying the product as oestrogens for systemic use, specifically conjugated natural oestrogens.

This classification determines formulary placement and regulatory categorisation within HRT options.

Formulation and marketed strengths

Which forms and strengths are sold?

Premarin is supplied as oral tablets in strengths of 0.3 mg, 0.625 mg and 1.25 mg.

Tablets are the main outpatient presentation and are usually packed in 28-tablet boxes in the UK market.

INN: Conjugated oestrogens.

ATC: G03CA57.

Excipients: Specific excipient lists are included in the MHRA PIL and SPC supplied with each pack; check the PIL for allergen information.

Indications and targeted use cases

Licensed indications

What is Premarin licensed to treat?

Premarin is licensed for hormone replacement therapy to relieve vasomotor and urogenital menopausal symptoms.

It is also licensed for prevention of postmenopausal osteoporosis, for hypoestrogenism due to ovarian failure and for palliative treatment in certain cancer settings.

Prescribers should document the indication on prescriptions and supply the MHRA patient information leaflet with the medicine.

Practical selection guidance

How do clinicians choose the right dose?

Starting doses for menopausal symptoms are commonly 0.3 mg or 0.625 mg daily and should be adjusted to the lowest effective dose for symptom control.

For osteoporosis prevention, 0.625 mg daily is a commonly referenced dose when oestrogen therapy is considered appropriate.

• Licensed indications: menopausal vasomotor symptoms, urogenital atrophy, osteoporosis prevention, hypoestrogenism and palliative oncology use.

Dosage regimens, administration and missed doses

Typical regimens and titration

What dosing schedules are used for Premarin?

Adults are commonly prescribed 0.3–1.25 mg daily depending on the indication and clinical response.

Menopausal symptom relief typically begins at 0.3 mg or 0.625 mg daily, titrating as necessary to symptom control at the lowest effective dose.

Both continuous and cyclic regimens are used; cyclic regimens such as three weeks on, one week off may be chosen for women with an intact uterus where a progestogen is also used.

Practical administration notes

How should patients take missed doses and what about overdoses?

Take the tablet orally at the same time each day to aid adherence.

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose; do not take a double dose to make up.

In overdose patients may experience nausea, vomiting or withdrawal bleeding and should seek medical attention.

Packaging and strengths

UK packaging and presentation

What does Premarin look like in the UK dispensary?

In the UK Premarin is typically supplied in boxes of 28 tablets at strengths of 0.3 mg, 0.625 mg and 1.25 mg manufactured by Pfizer.

Each pack is supplied with the MHRA‑approved patient information leaflet.

Contraindications and warnings

Absolute contraindications

Who must not take Premarin?

Absolute contraindications include undiagnosed vaginal bleeding and known or suspected breast or uterine cancer.

Active or a history of deep vein thrombosis, pulmonary embolism, recent stroke or myocardial infarction are absolute contraindications.

Severe liver dysfunction, pregnancy and breastfeeding are also absolute contraindications to use.

Relative risks

When should the pharmacist or prescriber pause and check before supply?

Relative risks include uncontrolled hypertension, diabetes, obesity, smoking, prolonged immobilisation and hereditary angioedema, all of which raise thromboembolic risk.

Pharmacists should use a private consultation to verify medical history, document answers and liaise with prescribers where appropriate.

• Points to check before supply: current unexplained bleeding; history of breast or uterine cancer; prior VTE, PE, stroke or MI; severe liver disease; pregnancy or breastfeeding.

Side effects, surveillance and reporting

Common adverse effects and patient signals

What side effects should patients expect and report?

Common adverse effects can include headache, breast pain or tenderness, abdominal cramps, bloating, vaginal spotting, nausea and mood changes.

Many adverse effects are mild or transient, but symptoms suggestive of thrombosis or severe neurological events require urgent medical review.

Monitoring and pharmacovigilance

How should patients be monitored while on Premarin?

Baseline and periodic checks should include blood pressure, weight and adherence to breast screening and cervical screening as applicable.

Suspected adverse drug reactions must be reported to the Yellow Card Scheme in the UK to support pharmacovigilance.

• Red flag symptoms: sudden chest pain or breathlessness, sudden unilateral leg swelling, sudden severe headache or visual disturbance — seek urgent care.

Drug interactions, hepatic and renal considerations

Key interactions to check

Which medicines affect Premarin and vice versa?

Medicines that induce hepatic enzymes, such as some anticonvulsants and rifampicin, can reduce oestrogen levels and reduce clinical effect.

Anticoagulant therapy may require monitoring adjustments when oestrogen therapy is started or stopped.

Interactions with thyroid replacement and systemic corticosteroids should be checked during medication reconciliation.

Organ impairment and dose adjustments

When is caution or avoidance needed?

Use with caution in renal impairment and consider dose adjustments for frail or elderly patients, who should receive the lowest effective dose.

Severe hepatic dysfunction is a contraindication to use and Premarin should be avoided in that setting.

Inducer: a drug that increases hepatic enzyme activity and can lower oestrogen plasma levels.

Inhibitor: a drug that reduces hepatic enzyme activity and may raise oestrogen exposure.

Clinical significance: enzyme inducers may reduce HRT efficacy; anticoagulant interactions can alter INR and bleeding risk.

Switching, comparators and alternatives

When to switch from Premarin

Why might a prescriber or patient choose to switch?

Switching can be due to side effects, patient preference, formulary availability or pursuit of lower‑risk delivery routes.

Document equivalence carefully when moving between conjugated oestrogens and estradiol products and ensure clinical oversight during transition.

Competitors and therapeutic alternatives

What are common alternatives to Premarin?

Alternatives include estriol preparations such as Ovestin and various estradiol products, including gels and transdermal patches.

Transdermal oestrogen routes are often favoured where reducing venous thromboembolism risk is a priority.

• Switching steps: review the indication and any history of VTE or cancer, choose an equivalent dose and arrange follow-up 4–12 weeks after the change.

Storage and handling

Storage

How should Premarin be stored?

Store Premarin tablets at room temperature between 15–30°C and protect from moisture and light.

Keep in the original packaging until use to retain the patient information leaflet and batch number for reference.

Travel

Patients travelling with Premarin should carry the original packaging and a copy of their prescription.

Counselling points and patient leaflets

Key counselling points at supply

What should be covered when handing over Premarin?

Explain the indication, expected onset of benefit and the prescribed dose and regimen.

Cover common side effects and emphasise red flags such as chest pain, sudden breathlessness or unilateral leg swelling.

Reinforce the importance of routine breast screening, smoking cessation and contraception if relevant for the patient.

Documentation and follow‑up

How should supply be documented and when should patients be reviewed?

Read the MHRA patient information leaflet supplied with the medicine, which includes Yellow Card reporting details.

Offer a medication review or follow-up contact within 4–12 weeks to assess tolerance and adherence.

• Counselling summary: indication, dose, missed‑dose instructions, common side effects, red flags, follow-up interval and Yellow Card reporting advice.

Delivery across the United Kingdom