Note: This document contains side effect information about conjugated estrogens. Some of the dosage forms listed on this page may not apply to the brand name Premarin.
Applies to conjugated estrogens: oral tablet
Other dosage forms:
Oral route (Tablet)
Unopposed estrogens increase the risk of endometrial cancer. Adding a progestin will reduce the risk of endometrial hyperplasia, which may be a precursor to endometrial cancer. Diagnostic measures should be undertaken to rule out malignancy in postmenopausal women with undiagnosed persistent or recurring abnormal genital bleeding. Estrogens with or without progestins should not be used for the prevention of cardiovascular disease or dementia. Increased risks of stroke and deep vein thrombosis in postmenopausal women (50 to 79 years of age) using estrogen alone have been reported. Increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50 to 79 years of age) using estrogens combined with progestins have been reported. An increased risk of developing probable dementia in postmenopausal women 65 years of age or older has also been reported in women receiving estrogen alone or estrogen combined with progestins. Risks should be assumed to be similar for other doses, combinations, and dosage forms of estrogens and progestins. Estrogens, with or without progestins, should be prescribed at the lowest effective doses and for the shortest duration possible.
Along with its needed effects, conjugated estrogens (the active ingredient contained in Premarin) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking conjugated estrogens:
Incidence not known
Some side effects of conjugated estrogens may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Incidence not known
Applies to conjugated estrogens: injectable powder for injection, oral tablet, vaginal cream
-HRT is associated with a 1.3 to 3-fold increased relative risk of developing VTE, i.e., deep vein thrombosis or pulmonary embolism. This event is more likely to occur in the first year of using HRT.
-The use of estrogen-only and estrogen-progestin therapy is associated with an up to 1.5 fold increased relative risk of ischemic stroke.
-The risk of hemorrhagic stroke is not increased during use of HRT. This relative risk is not dependent on age or on duration of use, but as the baseline risk is strongly age-dependent, the overall risk of stroke in women who use HRT will increase with age.
Common (1% to 10%): Hypertension, palpitation, vasodilation
Rare (less than 0.1%): Stroke
Postmarketing reports: Deep and superficial venous thrombosis, pulmonary embolism, thrombophlebitis, myocardial infarction, stroke
Common (1% to 10%): Acne, alopecia, hirsutism, pruritus, rash, skin discoloration, sweating, fungal dermatitis
Postmarketing reports: Chloasma or melasma (may persist when drug is discontinued), erythema multiforme, erythema nodosum, loss of scalp hair
Common (1% to 10%): Constipation, diarrhea, dyspepsia, eructation, flatulence, nausea
Uncommon (0.1% to 1%): Bloating, abdominal pain
Postmarketing reports: Vomiting, abdominal discomfort, abdominal distension
Common (1% to 10%): Pelvic pain, breast disorder, breast enlargement, breast neoplasm, breast pain, cervix disorder, dysmenorrhea, endometrial disorder, endometrial hyperplasia, leukorrhea, metrorrhagia, urinary tract infection, uterine fibroids enlarged, uterine spasm, abnormal uterine bleeding (breakthrough bleeding/spotting), vaginal dryness, vaginal hemorrhage, vaginal moniliasis, vaginitis
Uncommon (0.1% to 1%): Vaginal candidiasis, changes in menstrual flow, changes in cervical ectropion and secretion
Postmarketing reports: Increases in seize of uterine leiomyomata, change in cervical secretion, ovarian cancer, endometrial cancer, breast tenderness, breast discharge, galactorrhea, fibrocystic breast changes, breast cancer, gynecomastia in males
Common (1% to 10%): Hyperlipidemia, weight gain, increased appetite
Very rare (less than 0.01%): Hypocalcemia
Postmarketing reports: Increase or decrease in weight, glucose intolerance, aggravation of porphyria, increased triglycerides
Common (1% to 10%): Back pain, arthralgia, leg cramps, myalgia, muscle spasm
Common (1% to 10%): Headache, dizziness, paresthesia, migraine, hypertonia, insomnia, nervousness
Very rare (less than 0.01%): Exacerbation of chorea
Postmarketing reports: Exacerbation of epilepsy, dementia
Common (1% to 10%): Accidental injury, asthenia, chills, flu syndrome, pain, edema, peripheral edema, generalized edema, moniliasis
Postmarketing reports: Irritability
Common (1% to 10%): Depression, emotional liabilities, anxiety
Uncommon (0.1% to 1%): Changes in libido, mood disturbances
Common (1% to 10%): Chest pain, bronchitis, increased cough, pharyngitis, rhinitis, sinusitis, upper respiratory tract infection
Postmarketing reports: Exacerbation of asthma
Uncommon (0.1% to 1%): Gallbladder disease
Postmarketing reports: Cholestatic jaundice, pancreatitis, enlargement of hepatic hemangiomas, ischemic colitis
Uncommon (0.1% to 1%): Hypersensitivity
Rare (less than 0.1%): Anaphylactic/anaphylactoid reactions including urticaria and angioedema
Uncommon (0.1% to 1%): Intolerance to contact lenses, steepening of corneal curvature
Postmarketing reports: Retinal vascular thrombosis
Rare (0.01% to 0.1%): Breast cancer, ovarian cancer, fibrocystic breast changes, growth potentiation of benign meningioma.
Very rare (less than 0.01%): Endometrial cancer, enlargement of hepatic hemangiomas
-An up to 2-fold increased risk of having breast cancer diagnosed is reported in women taking combined estrogen-progestin therapy for more than 5 years.
-Any increased risk in users of estrogen-only therapy is substantially lower than that seen in users of estrogen-progestin combinations. The level of risk is dependent on the duration of use.
-Endometrial cancer risk is about 5 in every 1000 women with a uterus not using HRT.
-In women with a uterus, use of estrogen-only HRT is not recommended because it increases the risk of endometrial cancer.
-Depending on the duration of estrogen-only use and estrogen dose, the increase in risk of endometrial cancer varied from between 5 and 55 extra cases diagnosed in every 1000 women between the ages of 50 and 65.
-Adding a progestin to estrogen-only therapy for at least 12 days per cycle can prevent this increased risk. In the Million Women Study the use of five years of combined HRT did not increase risk of endometrial cancer.
-Long-term use of estrogen-only and combined estrogen-progestin HRT has been associated with a slightly increased risk of ovarian cancer. In the Million Women Study 5 years of HRT resulted in 1 extra case per 2500 users.
Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.
Source: Drugs.com Premarin