ENOVID-E 21

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ENOVID-E 21 (ENOVID-E 21).

How it works

Norethindrone is a progestin that suppresses gonadotropin release, inhibiting ovulation; mestranol is an estrogen that stabilizes endometrium and provides cycle control.

What the body does with it

Metabolism	Norethindrone: primarily hepatic via reduction and conjugation (CYP3A4 minor). Mestranol: demethylated to ethinyl estradiol; further metabolized by CYP3A4.
Excretion	73% renal (45% as unchanged norethindrone, 20% as conjugates, 8% as other metabolites), 27% fecal via bile. Enterohepatic recirculation accounts for 15% of total clearance.
Half-life	Terminal elimination half-life: 27–36 hours (mean 30.8 h). Steady-state reached after 5–7 days. Clinical context: allows once-daily dosing with stable estrogenic effect.
Protein binding	Norethindrone: 61% bound to albumin, 36% to SHBG (sex hormone-binding globulin). Ethinylestradiol: 97–98% bound (mainly albumin). Total protein binding for norethindrone: 97%.
Volume of Distribution	Norethindrone: Vd 3.6–4.5 L/kg (mean 4.0 L/kg). Ethinylestradiol: Vd 2.5–3.6 L/kg (mean 3.1 L/kg). Clinical meaning: extensive distribution into tissues, including breast, adipose, and reproductive organs.
Bioavailability	Oral: norethindrone 50–73% (first-pass effect reduces absolute bioavailability); ethinylestradiol 38–48% (first-pass metabolism in gut wall and liver).
Onset of Action	Oral: contraceptive effect requires 7 consecutive days. For ovulation suppression, first cycle suppression begins within 2–3 days; full contraceptive protection after 7 days. Missed dose: within 12 hours, no additional protection needed.
Duration of Action	Contraceptive effect persists for 7 days after last dose. For cycle control, withdrawal bleed occurs 2–3 days after placebo. Extended use (e.g., 21-day active phase) allows 7-day hormone-free interval.

Classification & Brands

Dosing & administration

One tablet (norethynodrel 2.5 mg, mestranol 0.1 mg) orally once daily for 21 consecutive days, followed by 7 days without medication. Repeat cycle.

Dosage form	TABLET
Renal impairment	No specific guidelines; use with caution in severe renal impairment (eGFR <30 mL/min/1.73 m²) due to potential fluid retention.
Liver impairment	Contraindicated in severe hepatic disease (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), use with caution and monitor liver function; no specific dose adjustment established.
Pediatric use	Not approved for use in pediatric patients; safety and efficacy not established.
Geriatric use	Not indicated for postmenopausal women; avoid use 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 ENOVID-E 21 (ENOVID-E 21).

Breastfeeding	Contraindicated during breastfeeding. Estrogens and progestins are excreted in breast milk with an M/P ratio approximately 0.5 for norethynodrel and mestranol. May reduce milk production and alter composition.
Teratogenic Risk	First trimester: Increased risk of cardiovascular defects and neural tube defects; second and third trimesters: Risk of feminization of male fetus, urogenital abnormalities, and potential long-term metabolic effects.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Cigarette smoking increases risk of serious cardiovascular side effects from oral contraceptive use. Risk increases with age and smoking ≥15 cigarettes per day. Women over 35 who smoke should not use this product.

Side Effect Profile

Serious Effects

Absolute Contraindications

Thrombophlebitis or thromboembolic disorders; history of deep vein thrombosis or pulmonary embolism; cerebrovascular or coronary artery disease; known or suspected breast cancer; estrogen-dependent neoplasia; undiagnosed abnormal genital bleeding; pregnancy; known or suspected pregnancy; liver tumors or active liver disease; hypersensitivity to any component.

Clinical Precautions

Precautions

Increased risk of thromboembolic disorders; discontinue if jaundice, visual disturbances, or migraine occurs; may cause fluid retention; monitor blood pressure; exacerbation of depression; liver enzyme alterations; glucose intolerance; cases of breakthrough bleeding; use with caution in patients with renal impairment.

Clinical Tips & Counseling

Drug interactions

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ENOVID-E 21

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ENOVID-E 21 (ENOVID-E 21).

How it works

Norethindrone is a progestin that suppresses gonadotropin release, inhibiting ovulation; mestranol is an estrogen that stabilizes endometrium and provides cycle control.

What the body does with it

Metabolism	Norethindrone: primarily hepatic via reduction and conjugation (CYP3A4 minor). Mestranol: demethylated to ethinyl estradiol; further metabolized by CYP3A4.
Excretion	73% renal (45% as unchanged norethindrone, 20% as conjugates, 8% as other metabolites), 27% fecal via bile. Enterohepatic recirculation accounts for 15% of total clearance.
Half-life	Terminal elimination half-life: 27–36 hours (mean 30.8 h). Steady-state reached after 5–7 days. Clinical context: allows once-daily dosing with stable estrogenic effect.
Protein binding	Norethindrone: 61% bound to albumin, 36% to SHBG (sex hormone-binding globulin). Ethinylestradiol: 97–98% bound (mainly albumin). Total protein binding for norethindrone: 97%.
Volume of Distribution	Norethindrone: Vd 3.6–4.5 L/kg (mean 4.0 L/kg). Ethinylestradiol: Vd 2.5–3.6 L/kg (mean 3.1 L/kg). Clinical meaning: extensive distribution into tissues, including breast, adipose, and reproductive organs.
Bioavailability	Oral: norethindrone 50–73% (first-pass effect reduces absolute bioavailability); ethinylestradiol 38–48% (first-pass metabolism in gut wall and liver).
Onset of Action	Oral: contraceptive effect requires 7 consecutive days. For ovulation suppression, first cycle suppression begins within 2–3 days; full contraceptive protection after 7 days. Missed dose: within 12 hours, no additional protection needed.
Duration of Action	Contraceptive effect persists for 7 days after last dose. For cycle control, withdrawal bleed occurs 2–3 days after placebo. Extended use (e.g., 21-day active phase) allows 7-day hormone-free interval.

Classification & Brands

Dosing & administration

One tablet (norethynodrel 2.5 mg, mestranol 0.1 mg) orally once daily for 21 consecutive days, followed by 7 days without medication. Repeat cycle.

Dosage form	TABLET
Renal impairment	No specific guidelines; use with caution in severe renal impairment (eGFR <30 mL/min/1.73 m²) due to potential fluid retention.
Liver impairment	Contraindicated in severe hepatic disease (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), use with caution and monitor liver function; no specific dose adjustment established.
Pediatric use	Not approved for use in pediatric patients; safety and efficacy not established.
Geriatric use	Not indicated for postmenopausal women; avoid use 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 ENOVID-E 21 (ENOVID-E 21).

Breastfeeding	Contraindicated during breastfeeding. Estrogens and progestins are excreted in breast milk with an M/P ratio approximately 0.5 for norethynodrel and mestranol. May reduce milk production and alter composition.
Teratogenic Risk	First trimester: Increased risk of cardiovascular defects and neural tube defects; second and third trimesters: Risk of feminization of male fetus, urogenital abnormalities, and potential long-term metabolic effects.
Fetal Monitoring