LOESTRIN FE 1/20

Clinical safety rating: caution

Comprehensive clinical and safety monograph for LOESTRIN FE 1/20 (LOESTRIN FE 1/20).

How it works

Combination oral contraceptive consisting of ethinyl estradiol and norethindrone acetate. Inhibits gonadotropin secretion (FSH, LH) via negative feedback on the hypothalamic-pituitary-ovarian axis, suppressing ovulation. Increases cervical mucus viscosity and alters endometrial structure, impeding sperm penetration and implantation.

What the body does with it

Metabolism	Ethinyl estradiol: primarily metabolized by CYP3A4; undergoes sulfation and glucuronidation. Norethindrone: metabolized primarily by reduction and conjugation (CYP3A4 minor role). Both undergo enterohepatic recycling.
Excretion	Norethindrone: 50-60% renal (as metabolites), 20-30% fecal. Ethinyl estradiol: 40-50% renal (as glucuronide conjugates), 30-40% fecal (as sulfate conjugates).
Half-life	Norethindrone: 6-9 hours (terminal). Ethinyl estradiol: 13-27 hours (terminal, mean 16 hours). Steady-state reached within 5-7 days.
Protein binding	Norethindrone: ~97% bound (mainly SHBG, also albumin). Ethinyl estradiol: ~98% bound (albumin, induces SHBG synthesis).
Volume of Distribution	Norethindrone: 2-5 L/kg. Ethinyl estradiol: 2-4 L/kg (increased water solubility vs estradiol).
Bioavailability	Norethindrone: 50-80% (oral). Ethinyl estradiol: 40-60% (oral, due to first-pass conjugation).
Onset of Action	Oral: Contraceptive effect requires 7 days of continuous dosing for full suppression of ovulation.
Duration of Action	24 hours after daily dosing; maintains suppression of gonadotropins and endometrial changes. Missed dose increases ovulation risk.

Classification & Brands

Dosing & administration

One tablet (norethindrone acetate 1 mg and ethinyl estradiol 20 mcg) orally once daily for 21 consecutive days, followed by one ferrous fumarate tablet (75 mg) orally once daily for 7 days.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment. Not studied in severe impairment (CrCl <30 mL/min); contraindicated in acute renal disease.
Liver impairment	Contraindicated in Child-Pugh class C. Use with caution in Child-Pugh class A or B; may increase risk of fluid retention and impaired metabolism.
Pediatric use	Not indicated for use before menarche. For postmenarchal adolescents: same dosing as adults (21 days active, 7 days ferrous fumarate).
Geriatric use	Not indicated for use after menopause. If prescribed in perimenopause, use lowest effective dose due to increased risk of thromboembolic events and cardiovascular disease.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for LOESTRIN FE 1/20 (LOESTRIN FE 1/20).

Breastfeeding	Small amounts of ethinyl estradiol and progestins are excreted in human milk. M/P ratio not established. Use may reduce milk production, particularly with high-dose estrogen. Breastfeeding women should avoid combination hormonal contraceptives until weaning or use progestin-only methods.
Teratogenic Risk	First trimester: Combination hormonal contraceptives are not associated with an increased risk of major birth defects when inadvertently taken. Second and third trimesters: No known risk of fetal abnormalities; however, use during pregnancy is not indicated. Postnatal: No evidence of long-term adverse effects from inadvertent exposure.

Warnings & precautions

■ FDA Black Box Warning

Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptives. Risk increases with age (especially women >35 years) and number of cigarettes smoked. Women >35 and who smoke should not use this product.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Current or history of thrombosis (DVT, PE)","Cerebrovascular or coronary artery disease","Known or suspected breast cancer","Undiagnosed abnormal uterine bleeding","Known or suspected pregnancy","Liver neoplasia or active liver disease","Age >35 and smoking","Hypersensitivity to components"]

Clinical Precautions

Precautions

["Increased risk of thromboembolic disorders (e.g., DVT, PE, stroke, MI)","Cerebrovascular disease","Carcinoma of the breast and reproductive organs","Liver disease (hepatic adenoma, hepatocellular carcinoma)","Elevated blood pressure","Gallbladder disease","Carbohydrate/lipid metabolic effects","Hereditary angioedema","Chloasma","Ocular lesions (retinal thrombosis)","Depression","Reduced efficacy with concomitant enzyme inducers"]

Clinical Tips & Counseling

Drug interactions

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LOESTRIN FE 1/20

Clinical safety rating: caution

Comprehensive clinical and safety monograph for LOESTRIN FE 1/20 (LOESTRIN FE 1/20).

How it works

What the body does with it

Metabolism	Ethinyl estradiol: primarily metabolized by CYP3A4; undergoes sulfation and glucuronidation. Norethindrone: metabolized primarily by reduction and conjugation (CYP3A4 minor role). Both undergo enterohepatic recycling.
Excretion	Norethindrone: 50-60% renal (as metabolites), 20-30% fecal. Ethinyl estradiol: 40-50% renal (as glucuronide conjugates), 30-40% fecal (as sulfate conjugates).
Half-life	Norethindrone: 6-9 hours (terminal). Ethinyl estradiol: 13-27 hours (terminal, mean 16 hours). Steady-state reached within 5-7 days.
Protein binding	Norethindrone: ~97% bound (mainly SHBG, also albumin). Ethinyl estradiol: ~98% bound (albumin, induces SHBG synthesis).
Volume of Distribution	Norethindrone: 2-5 L/kg. Ethinyl estradiol: 2-4 L/kg (increased water solubility vs estradiol).
Bioavailability	Norethindrone: 50-80% (oral). Ethinyl estradiol: 40-60% (oral, due to first-pass conjugation).
Onset of Action	Oral: Contraceptive effect requires 7 days of continuous dosing for full suppression of ovulation.
Duration of Action	24 hours after daily dosing; maintains suppression of gonadotropins and endometrial changes. Missed dose increases ovulation risk.

Classification & Brands

Dosing & administration

One tablet (norethindrone acetate 1 mg and ethinyl estradiol 20 mcg) orally once daily for 21 consecutive days, followed by one ferrous fumarate tablet (75 mg) orally once daily for 7 days.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild to moderate renal impairment. Not studied in severe impairment (CrCl <30 mL/min); contraindicated in acute renal disease.
Liver impairment	Contraindicated in Child-Pugh class C. Use with caution in Child-Pugh class A or B; may increase risk of fluid retention and impaired metabolism.
Pediatric use	Not indicated for use before menarche. For postmenarchal adolescents: same dosing as adults (21 days active, 7 days ferrous fumarate).
Geriatric use	Not indicated for use after menopause. If prescribed in perimenopause, use lowest effective dose due to increased risk of thromboembolic events and cardiovascular disease.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for LOESTRIN FE 1/20 (LOESTRIN FE 1/20).

Breastfeeding	Small amounts of ethinyl estradiol and progestins are excreted in human milk. M/P ratio not established. Use may reduce milk production, particularly with high-dose estrogen. Breastfeeding women should avoid combination hormonal contraceptives until weaning or use progestin-only methods.
Teratogenic Risk	First trimester: Combination hormonal contraceptives are not associated with an increased risk of major birth defects when inadvertently taken. Second and third trimesters: No known risk of fetal abnormalities; however, use during pregnancy is not indicated. Postnatal: No evidence of long-term adverse effects from inadvertent exposure.