Adult: 10-50 mcg daily, usually on a cyclical basis. Initial estrogen therapy should be followed by a combined estrogen and progestogen therapy.
Oral Postmenopausal symptoms due to estrogen deficiency
Adult: 10-50 mcg daily for 21 days, repeated after a 7-day tablet-free period, to be given with a progestogen for 12-14 days per cycle in women with an intact uterus or in endometriosis when endometrial foci may be present despite hysterectomy. Not recommended to add a progestogen in women without a uterus, who did not have endometriosis diagnosed.
Oral Prophylaxis of osteoporosis in postmenopausal women
Adult: In women at high risk of future fractures who are intolerant of, or contraindicated for, other osteoporosis-preventing therapies: 10-50 mcg daily for 21 days, repeated after a 7-day tablet-free period, to be given with a progestogen for 12-14 days per cycle in women with an intact uterus or in endometriosis when endometrial foci may be present despite hysterectomy. Not recommended to add a progestogen in women without a uterus, who did not have endometriosis diagnosed.
Oral Palliative treatment of prostatic carcinoma
Adult: 150-1,500 mcg daily.
Oral Menstrual disorders
Adult: 20-50 mcg daily from day 5-25 of each cycle; given together with a progestogen, added either throughout the cycle or from day 15-25.
Administration
May be taken with or without food.
Contraindications
Active or recent arterial thromboembolic disease (e.g. angina, MI); current or previous idiopathic venous thromboembolism (e.g. DVT, pulmonary embolism); known, previous, or suspected breast cancer or other estrogen dependent tumours (e.g. endometrial cancer); untreated endometrial hyperplasia, undiagnosed abnormal vaginal bleeding; acute or active liver disease or a history of liver disease wherein LFTs have failed to return to normal; porphyria. Pregnancy and lactation. Concomitant use with ombitasvir/paritaprevir/ritonavir, dasabuvir, glecaprevir/pibrentasvir, and sofosbuvir/velpatasvir/voxilaprevir.
Special Precautions
Patients with asthma, diabetes mellitus with or without vascular involvement, cholelithiasis, uterine fibroids (e.g. leiomyoma), endometriosis, hypertension, hypertriglyceridaemia, otosclerosis, thyroid disorders; history of seizures or epilepsy, severe headache or migraine, breast nodules or fibrocystic disease; diseases which may be exacerbated by fluid retention (e.g. CV disease); hereditary or acquired angioedema; risk factors for venous thromboembolism (e.g. family or personal history, obesity [BMI >30 kg/m2], SLE, presence of antiphospholipid bodies, known thrombophilic states, prolonged immobilisation, major trauma or surgery). Predisposition to estrogen-dependent tumours (e.g. breast cancer in first-degree relative). Hepatic and renal impairment.
Adverse Reactions
Significant: Break-through bleeding, spotting; exacerbation of endometriosis; venous thromboembolism (e.g. DVT, pulmonary embolism), hypercalcaemia, increased thyroid binding globulin causing increased circulating total thyroid hormone. Rarely, increased triglycerides leading to pancreatitis; increased risk of endometrial, breast or ovarian cancer, endometrial hyperplasia (prolonged use). Cardiac disorders: MI. Endocrine disorders: Reduced glucose tolerance. Eye disorders: Contact lens intolerance. Gastrointestinal disorders: Nausea, vomiting. Hepatobiliary disorders: Cholelithiasis, cholestatic jaundice. Metabolism and nutrition disorders: Na and water retention. Nervous system disorders: Headache, migraine, dementia. Psychiatric disorders: Mood changes. Reproductive system and breast disorders: Breast tenderness, pain, enlargement, and secretion. Gyncaecomastia, feminisation, testicular atrophy, impotence (men). Skin and subcutaneous tissue disorders: Chloasma, erythema multiforme, erythema nodosum, rash. Vascular disorders: Hypertension.
Perform routine physical examination that includes blood pressure, breast and pelvic exam, and mammogram. Asses for signs of endometrial cancer in female patients with a uterus.
Drug Interactions
May increase metabolism with CYP450 enzyme inducers including anticonvulsants (e.g. phenobarbital, phenytoin, carbamazepine), anti-infectives (e.g. rifampicin, rifabutin, nevirapine, efavirenz), modafinil. May reduce the effects of insulin or hypoglycaemic drugs, anticoagulants (e.g. warfarin, phenindione, acenocoumarol). May inhibit the metabolism and reduce the clearance of theophylline. Decreased serum concentrations of lamotrigine. Increased risk of imipramine toxicity (doses >50 mcg daily). Potentially Fatal: Increased risk of ALT elevations in concomitant use with ombitasvir/paritaprevir/ritonavir, dasabuvir, glecaprevir/pibrentasvir and sofosbuvir/velpatasvir/voxilaprevir.
Food Interaction
May induce metabolism with St. John's Wort.
Action
Description: Mechanism of Action: Ethinylestradiol is a synthetic estrogen with actions similar to those of estradiol. In post-menopausal women, it increases estrogen levels, relieves the associated symptoms, and prevents bone loss following menopause or ovariectomy due to increasing bone turnover and a decline in bone mass. Pharmacokinetics: Absorption: Rapidly and completely absorbed from the gastrointestinal tract. Bioavailability: 20-65%. Time to peak plasma concentration: 2-3 hours (initial); 12 hours (secondary). Distribution: Rapidly distributed throughout most body tissues. Enters breast milk. Volume of distribution: 2.2-3.8 L/kg. Plasma protein binding: >90%, mainly to albumin. Metabolism: Metabolised in the liver via aromatic hydroxylation by CYP3A4 into 2-hydroxyethinylestradiol and various conjugated metabolites. Excretion: Via urine (60%) and faeces (40%), as metabolites. Terminal elimination half-life: 5-30 hours.
Chemical Structure
Ethinylestradiol Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5991, Ethinylestradiol. https://pubchem.ncbi.nlm.nih.gov/compound/Ethinylestradiol. Accessed Apr. 27, 2022.
L02AA03 - ethinylestradiol ; Belongs to the class of estrogens. G03CA01 - ethinylestradiol ; Belongs to the class of natural and semisynthetic estrogens used in estrogenic hormone preparations.
References
Anon. Ethinylestradiol. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 06/10/2020.Buckingham R (ed). Ethinylestradiol. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/10/2020.Ethinylestradiol Tablets BP 1 mg (UCB Pharma Ltd). MHRA. https://products.mhra.gov.uk. Accessed 06/10/2020.Ethinylestradiol Tablets BP 50 mcg (UCB Pharma Ltd). MHRA. https://products.mhra.gov.uk. Accessed 06/10/2020.Joint Formulary Committee. Ethinylestradiol. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/10/2020.New Zealand Medical and Scientific Ltd. Ethinyloestradiol 10 mcg Tablets data sheet 14 November 2016. Medsafe. http://www.medsafe.govt.nz. Accessed 06/10/2020.
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