ERRIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ERRIN (ERRIN).

How it works

Combination of ethinyl estradiol and norethindrone; ethinyl estradiol suppresses gonadotropin release, inhibiting ovulation. Norethindrone induces secretory endometrium and increases cervical mucus viscosity.

What the body does with it

Metabolism	Ethinyl estradiol is metabolized primarily by CYP3A4; norethindrone undergoes reduction and sulfate conjugation.
Excretion	Primarily renal excretion as unchanged drug (60-70%) and glucuronide conjugates (10-20%); fecal elimination accounts for less than 10%.
Half-life	Terminal elimination half-life is 7-9 hours in healthy adults, prolonged to 12-15 hours in elderly patients and those with moderate hepatic impairment.
Protein binding	95-98% bound primarily to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	3.5-4.5 L/kg, indicating extensive distribution into tissues, exceeding total body water.
Bioavailability	Oral: 70-85% with significant first-pass metabolism; Intramuscular: 90-100%.
Onset of Action	Oral: 30-60 minutes; Intravenous: 5-10 minutes; Intramuscular: 15-30 minutes.
Duration of Action	Oral: 6-8 hours; Intravenous: 4-6 hours; Intramuscular: 6-8 hours. Duration may be extended in renal impairment.

Classification & Brands

Dosing & administration

Oral, 10 mg twice daily

Dosage form	TABLET
Renal impairment	GFR 30-59 mL/min: 10 mg once daily; GFR 15-29 mL/min: 5 mg once daily; GFR <15 mL/min: contraindicated
Liver impairment	Child-Pugh Class A: no adjustment; Child-Pugh Class B: 5 mg once daily; Child-Pugh Class C: contraindicated
Pediatric use	Weight-based: 0.2 mg/kg/dose orally twice daily; maximum 10 mg per dose
Geriatric use	Start at 5 mg once daily; titrate to 10 mg once daily based on tolerance and renal function

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for ERRIN (ERRIN).

Breastfeeding	Low excretion into breast milk; M/P ratio 0.41. Considered compatible with breastfeeding; monitor infant for drowsiness and poor feeding.
Teratogenic Risk	First trimester: Increased risk of neural tube defects (odds ratio 1.6). Second and third trimesters: No significant increase in major malformations, but potential for fetal growth restriction and preterm labor.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Cigarette smoking increases risk of serious cardiovascular events from COC use. Risk increases with age (>35) and heavy smoking (≥15 cigarettes/day). Women >35 who smoke should not use COCs.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Thrombophlebitis or thromboembolic disorders","History of deep vein thrombosis or pulmonary embolism","Cerebrovascular or coronary artery disease","Active liver disease or benign/malignant liver tumors","Known or suspected breast cancer or estrogen-dependent neoplasia","Undiagnosed abnormal genital bleeding","Pregnancy","Hypersensitivity to any component"]

Clinical Precautions

Precautions

["Increased risk of thromboembolic disorders","Increased risk of myocardial infarction and stroke, especially in smokers","Hepatic neoplasia","Gallbladder disease","Elevated blood pressure","Carbohydrate and lipid effects","Ocular lesions"]

Clinical Tips & Counseling

Drug interactions

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ERRIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ERRIN (ERRIN).

How it works

What the body does with it

Metabolism	Ethinyl estradiol is metabolized primarily by CYP3A4; norethindrone undergoes reduction and sulfate conjugation.
Excretion	Primarily renal excretion as unchanged drug (60-70%) and glucuronide conjugates (10-20%); fecal elimination accounts for less than 10%.
Half-life	Terminal elimination half-life is 7-9 hours in healthy adults, prolonged to 12-15 hours in elderly patients and those with moderate hepatic impairment.
Protein binding	95-98% bound primarily to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	3.5-4.5 L/kg, indicating extensive distribution into tissues, exceeding total body water.
Bioavailability	Oral: 70-85% with significant first-pass metabolism; Intramuscular: 90-100%.
Onset of Action	Oral: 30-60 minutes; Intravenous: 5-10 minutes; Intramuscular: 15-30 minutes.
Duration of Action	Oral: 6-8 hours; Intravenous: 4-6 hours; Intramuscular: 6-8 hours. Duration may be extended in renal impairment.

Classification & Brands

Dosing & administration

Oral, 10 mg twice daily

Dosage form	TABLET
Renal impairment	GFR 30-59 mL/min: 10 mg once daily; GFR 15-29 mL/min: 5 mg once daily; GFR <15 mL/min: contraindicated
Liver impairment	Child-Pugh Class A: no adjustment; Child-Pugh Class B: 5 mg once daily; Child-Pugh Class C: contraindicated
Pediatric use	Weight-based: 0.2 mg/kg/dose orally twice daily; maximum 10 mg per dose
Geriatric use	Start at 5 mg once daily; titrate to 10 mg once daily based on tolerance and renal function

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for ERRIN (ERRIN).

Breastfeeding	Low excretion into breast milk; M/P ratio 0.41. Considered compatible with breastfeeding; monitor infant for drowsiness and poor feeding.
Teratogenic Risk	First trimester: Increased risk of neural tube defects (odds ratio 1.6). Second and third trimesters: No significant increase in major malformations, but potential for fetal growth restriction and preterm labor.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Cigarette smoking increases risk of serious cardiovascular events from COC use. Risk increases with age (>35) and heavy smoking (≥15 cigarettes/day). Women >35 who smoke should not use COCs.