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Conjugated oestrogens equine oral

Updated 2 Feb 2023 | Oestrogens and HRT


Tablets containing conjugated oestrogens, equine

Drugs List

  • conjugated oestrogens 1.25mg tablets
  • conjugated oestrogens 300microgram tablets
  • conjugated oestrogens 625microgram tablets
  • PREMARIN 1.25mg tablets
  • PREMARIN 300microgram tablets
  • PREMARIN 625microgram tablets
  • Therapeutic Indications


    Replacement therapy for oestrogen deficiency symptoms
    Secondary prophylaxis of postmenopausal osteoporosis where risk of fracture

    All strengths
    Hormone replacement therapy (HRT) for oestrogen deficiency symptoms in postmenopausal women.

    625 micrograms and 1.25 mg tablets only
    Prevention of osteoporosis in postmenopausal women at a high risk of fractures and who are intolerant or contraindicated for drugs indicated for the prevention of osteoporosis.



    Treatment of oestrogen deficiency symptoms
    0.3 mg to 1.25 mg daily depending on response. Continuous administration is recommended.

    Prophylaxis of osteoporosis
    0.625 mg to 1.25 mg daily. The minimum effective dose for most patients is 0.625 mg daily.


    Treatment of oestrogen deficiency symptoms
    0.3 mg to 1.25 mg daily depending on response. Continuous administration is recommended.

    Prophylaxis of osteoporosis
    0.625 mg to 1.25 mg daily. The minimum effective dose for most patients is 0.625 mg daily.

    Additional Dosage Information

    Starting or Changing Treatment
    For postmenopausal women not currently receiving hormone replacement therapy or women receiving continuous combined hormone replacement therapy, treatment may begin at any time.

    In women transferring from a sequential hormone replacement therapy regime, treatment should begin the day following completion of the previous regimen.

    Missed Tablets
    If a tablet is forgotten, it should be taken as soon as the patient remembers, therapy should then continue as before. If more than one tablet has been missed, only the most recent tablet should be taken, the patient should not take multiple doses.

    Missed tablets may cause breakthrough bleeding in women with a uterus.


    Children under 18 years
    Abnormal liver function test
    Acute hepatic disorder
    Breast cancer
    Deep vein thrombosis
    Familial conjugated hyperbilirubinaemias
    Hereditary fructose intolerance
    History of breast cancer
    History of hormone dependent neoplasm
    History of thromboembolic disorder without anticoagulant therapy
    History of venous thromboembolism
    Lupus anticoagulant
    Oestrogen dependent neoplasm
    Protein C deficiency disease
    Protein S deficiency disease
    Pulmonary embolism
    Recent arterial thromboembolic disorder
    Uncontrolled endometrial hyperplasia
    Undiagnosed gynaecological haemorrhage

    Precautions and Warnings

    Body mass index above 30kg per square metre
    Family history of breast cancer
    Family history of venous thromboembolism
    History of recurrent spontaneous abortion
    Predisposition to thromboembolic disease
    Prolonged immobilisation
    Recent surgery
    Recent trauma
    Severe headache
    Cardiac impairment
    Diabetes mellitus
    Endometrial hyperplasia
    Epileptic disorder
    Gall bladder disorder
    Glucose-galactose malabsorption syndrome
    Hepatic adenoma
    Hepatic impairment
    History of chloasma
    History of endometrial hyperplasia
    History of thromboembolic disorder
    Lactose intolerance
    Malignant melanoma
    Multiple sclerosis
    Renal impairment
    Sickle cell disease
    Systemic lupus erythematosus
    Uterine fibroids

    Patients on thyroid replacement therapy may require increased doses
    Risk of pancreatitis in individuals with hypertriglyceridaemia
    Add progestogen for 12-14 days each cycle for those with an intact uterus
    Assess family medical history prior to commencing treatment
    Exclude breast cancer before treatment
    Exclude oestrogen dependent neoplasm before treatment
    Not all available strengths are licensed for all indications
    Contains lactose
    Preparation contains sucrose
    Some formulations contain sunset yellow (E110); may cause allergic reaction
    Do breast & pelvic exam. before & during treatment if clinically indicated
    Exclude pregnancy prior to initiation of treatment
    Abnormal and/or irregular bleeding should be investigated
    Advise patients of risks/benefits & review need for treatment regularly
    Discontinue treatment if patient develops seizures
    Monitor hepatic function in patients with hepatic impairment
    Advise patient of thromboembolic symptoms and to report them if they occur
    Advise patient that changes in their breasts should be reported to Dr/nurse
    Discontinue at the onset of severe depression
    Increased risk of VTE during travel involving >5hr immobilisation
    Uterine fibroids may increase in size
    May interfere with certain laboratory measurements
    Discontinue 4 - 6 weeks before major surgery
    Advise patient to seek advice at first indications of pregnancy
    Discontinue at first signs of thrombophlebitis or thromboembolism
    Discontinue if cholestasis develops
    Discontinue if first appearance of migraine or severe or frequent headache
    Discontinue if jaundice or other evidence of hepatic impairment occurs
    Discontinue if severe abdominal symptoms develop
    Discontinue if significant rise in blood pressure occurs
    Discontinue if sudden pain in the chest occurs
    Discontinue if symptoms due to endometriosis are exacerbated
    Maintain treatment at the lowest effective dose
    Advise patient not to take St John's wort concurrently
    Advise patient grapefruit products may increase plasma level
    Female: Not for contraception.Use non-hormonal contraception, if required
    Advise patient of increased risk of breast cancer vs benefits of HRT
    Intolerance to contact lenses may occur

    Only for use in the treatment of menopausal symptoms which adversely affect the quality of life. Treatment should be reviewed annually and only continued if the benefits outweigh the risks.

    Investigations including mammography should be carried out in accordance with currently accepted screening practices, modified according to the clinical needs of the individual.

    Examinations to rule out endometrial abnormalities should be undertaken at regular intervals. Prolonged monotherapy with oestrogens increases the risk of endometrial hyperplasia and carcinoma in postmenopausal women unless supplemented by sequential administration of a progestogen to protect the endometrium. The addition of a progestogen for at least 12 days of the cycle in non-hysterectomised women greatly reduces this risk. Unless there is a previous diagnosis of endometriosis it is not recommended to add a progestogen in hysterectomised women.

    Patients with end stage renal disease should be closely monitored since the circulating level of the active ingredients will be increased.

    Pregnancy and Lactation


    Hormone replacement therapy is contraindicated during pregnancy.

    Should pregnancy occur, treatment should be discontinued immediately.

    An increase in the expected frequency of cardiovascular defects, eye and ear abnormalities and Down's syndrome has been found with oestrogens as a group in the newborn when exposed to these in the womb (Briggs, 2011). However, some studies have failed to find a relationship with cardiovascular defects and non-genital malformations.

    Development alterations in the psychosexual performance of boys have been attributed to exposure to estradiol and progestogen in the womb. Males who have been exposed to estradiol and progestogen have demonstrated a trend to have less heterosexual characteristics and fewer masculine interests than males which have not been exposed to these hormones prenatally.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Hormone replacement therapy is contraindicated during breastfeeding.

    Estradiol has been used to suppress postpartum breast engorgement in patients who do not desire to breastfeed (Hale, 2010). Oestrogenic agents demonstrate lower infant weight gain, decreased milk production and decreased composition of nitrogen and protein content of human milk (Briggs, 2011). Even though the extent of these changes is low, the changes in milk production and composition may be of nutritional importance in malnourished mothers. Because of the reasons mentioned above the use of this medication during breastfeeding should be avoided.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    Encourage patients to participate in the national breast cancer screening programme and the national cervical cancer screening programme as appropriate for their age. Breast awareness should also be encouraged and patients advised to report any changes in their breasts to their doctor or nurse.

    Advise patients to contact their doctor if they are aware of a potential thromboembolic symptom (e.g. painful swelling of a leg, sudden pain in the chest, dyspnoea).

    Patients should be advised of the increased risks of diagnosis of breast cancer versus the benefits of HRT.

    Advise patients not to self-medicate with St John's Wort during HRT.

    Advise patient grapefruit products may increase the plasma level of the drug.

    Side Effects

    "Spotting" bleeding
    Abdominal pain
    Aggravation of porphyria
    Anaphylactoid reaction
    Breakthrough bleeding
    Breast enlargement
    Breast pain
    Breast secretion
    Breast tenderness
    Cervical erosion
    Change in amount of cervical secretion
    Change in carbohydrate metabolism
    Change in menstrual flow
    Changes in libido
    Cholestatic jaundice
    Decreased glucose tolerance
    Deep vein thrombosis (DVT)
    Endometrial hyperplasia
    Enlargement of hepatic haemangiomas
    Erythema multiforme
    Erythema nodosum
    Exacerbation of chorea
    Exacerbation of epilepsy
    Exacerbation of hypocalcaemia
    Exacerbation of otosclerosis
    Exacerbation of pre-existing asthma
    Fibrocystic breast changes
    Fluid retention
    Gallbladder disease
    Gynaecomastia in older men
    Haemorrhagic eruption
    Hypersensitivity reactions
    Increase in plasma triglyceride concentration
    Increased blood pressure
    Increased risk of breast cancer
    Increased risk of endometrial cancer
    Increased risk of oestrogen-dependent neoplasms
    Increased size of uterine fibroids
    Intolerance to contact lenses
    Irregular uterine bleeding
    Ischaemic colitis
    Leg cramps
    Mood changes
    Myocardial infarction
    Ovarian cancer
    Pelvic pain
    Premenstrual-like syndrome
    Pulmonary embolism
    Retinal vascular thrombosis
    Sodium retention
    Uterine bleeding
    Vaginal candidiasis
    Vascular purpura
    Venous thrombosis
    Weight changes

    Effects on Laboratory Tests

    Hormone replacement therapy, especially oestrogen-progestogen combined treatment may increase the density of mammographic images and adversely effect the detection of breast cancer.

    The use of oestrogen may influence the laboratory results of certain endocrine tests and liver enzymes.


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: August 2014

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press Accessed on August 14, 2014.

    Medications and Mothers' Milk, 14th Edition (2010) Hale, T. Hale Publishing, Amarillo, Texas.

    Summary of Product Characteristics: Premarin 0.3 mg tablets. Pfizer Ltd. Revised August 2016.
    Summary of Product Characteristics: Premarin 0.625 mg tablets. Pfizer Ltd. Revised August 2016.
    Summary of Product Characteristics: Premarin 1.25 mg tablets. Pfizer Ltd. Revised August 2016.

    The Renal Drug Handbook. 3rd edition. (2009) ed. Ashley, C and Currie, Radcliffe Publishing Ltd, Abingdon.

    MHRA Drug Safety Update: Hormone-replacement therapy. Dated: September 2007.
    Last accessed: 19 December 2011

    NAPOS. The drug database for acute porphyria.
    Available at: Conjugated estrogens.
    Last revised: September 2009
    Last accessed: August 19, 2014

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