N.E.E. 1/35 21
Clinical safety rating
cautionComprehensive clinical and safety monograph for N.E.E. 1/35 21 (N.E.E. 1/35 21).
Combination estrogen-progestin contraceptive: ethinyl estradiol (estrogen) and norethindrone (progestin). Suppresses gonadotropin (FSH, LH) release via negative feedback, inhibiting ovulation; increases cervical mucus viscosity to impede sperm penetration; alters endometrial development to reduce implantation likelihood.
| Metabolism | Ethinyl estradiol: primarily hepatic via CYP3A4, undergoes conjugation (glucuronidation and sulfation). Norethindrone: hepatic reduction and conjugation, also metabolized by CYP3A4. Both undergo enterohepatic recirculation. |
| Excretion | Norethindrone (NET) and ethinyl estradiol (EE) are excreted primarily in urine (~50-60% as metabolites) and feces (~30-40% as metabolites); less than 1% excreted unchanged. |
| Half-life | Norethindrone: terminal half-life 7-8 hours; Ethinyl estradiol: terminal half-life 12-14 hours (with enterohepatic recycling). Clinically, steady state achieved after 5-7 days. |
| Protein binding | Norethindrone: ~97% bound (albumin, SHBG); Ethinyl estradiol: ~98% bound (albumin). |
| Volume of Distribution | Norethindrone: Vd 4-5 L/kg; Ethinyl estradiol: Vd 3-4 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: Norethindrone ~64%; Ethinyl estradiol ~45% (first-pass metabolism). |
| Onset of Action | Oral: contraceptive effect requires 7 days of continuous dosing for full suppression of ovulation; immediate effect on cervical mucus within 24 hours. |
| Duration of Action | Contraceptive protection lasts for the 21-day dosing period; after last pill, ovulation returns typically within 1-2 weeks (range 7–21 days). |
| Molecular Weight | 340.46 |
One tablet orally once daily for 21 days, followed by 7 days off.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required. Use with caution in severe impairment. |
| Liver impairment | Contraindicated in Child-Pugh Class B or C (moderate to severe hepatic impairment). |
| Pediatric use | Not indicated in prepubertal children; use only after menarche per adult dosing. |
| Geriatric use | Not indicated for contraception postmenopausal; use lowest effective dose for hormone therapy if applicable. |
| 1st trimester | Contraindicated: Risk of birth defects, CVS anomalies, and fetal harm. Pregnancy should be excluded before initiation. |
| 2nd trimester | Contraindicated: Continued use may cause fetal harm, including virilization of female fetuses. |
| 3rd trimester | Contraindicated: Risk of fetal harm, including reduced birth weight and possible hormonal effects. |
Clinical note
Comprehensive clinical and safety monograph for N.E.E. 1/35 21 (N.E.E. 1/35 21).
| Placental transfer | Yes, the drug crosses the placenta; both ethinyl estradiol and norethindrone are transferred. |
| Breastfeeding | Excreted in breast milk; may reduce milk production and quality. Use only if benefits outweigh risks; monitor infant for jaundice and growth. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | N.E.E. 1/35 21 (norethindrone/ethinyl estradiol) is contraindicated in pregnancy. First trimester: No increased risk of major birth defects based on population data, but should not be used once pregnancy is confirmed. Second and third trimesters: Known risks include feminization of male fetus, cardiovascular and skeletal abnormalities, and potential for long-term effects on the child. Immediate discontinuation if pregnancy occurs. |
| Fetal Monitoring | Monitor blood pressure, renal function, hepatic function, and glucose tolerance during pregnancy if inadvertent exposure. If used postpartum, monitor infant for jaundice and growth. No routine fetal monitoring recommended except standard prenatal care. In case of exposure, consider early ultrasound for fetal anatomy. |
| Fertility Effects | Reversible suppression of ovulation. Normal fertility typically returns within one cycle after discontinuation. No permanent negative impact on fertility. Use does not increase risk of infertility or future reproductive problems. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age (especially >35 years) and with heavy smoking (>15 cigarettes/day). Women over 35 who smoke should not use this product.
| Serious Effects |
PregnancyThrombophlebitis or thromboembolic disordersKnown or suspected breast cancerUndiagnosed abnormal genital bleedingBenign or malignant liver tumors (current or history)Active liver disease (e.g., hepatitis) or impaired liver function
| Precautions | Increased risk of thromboembolic disorders (e.g., DVT, PE, stroke, MI), Cigarette smoking significantly increases cardiovascular risk (see boxed warning), Elevated blood pressure, Hepatic neoplasia (benign and malignant) reported with long-term use, Gallbladder disease, Carbohydrate and lipid metabolic effects (monitor in prediabetic/diabetic patients), Headache (including migraine), discontinue if new or worsening pattern, Bleeding irregularities (breakthrough bleeding, amenorrhea), Chloasma (may persist after discontinuation), Retinal thrombosis (discontinue if unexplained vision loss) |
| Food/Dietary | Avoid grapefruit and grapefruit juice during treatment due to potential increase in estrogen exposure and risk of adverse effects. No other significant food interactions reported. |
| Clinical Pearls | N.E.E. 1/35 21 is a monophasic combined oral contraceptive containing 1 mg norethindrone and 35 mcg ethinyl estradiol. It can be used for cycle control and dysmenorrhea. Missed pill management: if one pill is missed, take it as soon as remembered; if two or more are missed, use backup contraception for 7 days. Consider potential drug interactions with rifampin, certain anticonvulsants, and St. John's Wort which may reduce efficacy. |
| Patient Advice | Take one tablet daily at the same time each day for 21 days, then 7 days off. · If you miss a pill, take it as soon as you remember. If more than one pill is missed, use backup contraception. · This medication does not protect against sexually transmitted infections. · Common side effects include nausea, headache, breast tenderness, and breakthrough bleeding. · Smoking increases risk of serious cardiovascular side effects; avoid smoking, especially if over 35. · Report symptoms of blood clots such as leg pain/swelling, chest pain, or sudden shortness of breath. |
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