ENPRESSE-21
Clinical safety rating
cautionComprehensive clinical and safety monograph for ENPRESSE-21 (ENPRESSE-21).
Combination oral contraceptive; suppresses gonadotropin release via estrogen-progestin negative feedback, preventing ovulation; alters cervical mucus and endometrial lining to inhibit sperm penetration and implantation.
| Metabolism | Ethinyl estradiol is metabolized primarily via CYP3A4 hydroxylation; drospirenone is metabolized via CYP3A4 to inactive metabolites. |
| Excretion | Renal excretion of unchanged drug accounts for approximately 30-40% of the dose; hepatic metabolism accounts for the remainder, with metabolites eliminated in bile and feces. |
| Half-life | Terminal elimination half-life is 8-10 hours; this supports once-daily dosing and reaches steady state within 2-3 days. |
| Protein binding | 98-99% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd is 0.8-1.0 L/kg, indicating distribution into total body water. |
| Bioavailability | Absolute bioavailability after oral administration is 60-70% due to first-pass metabolism. |
| Onset of Action | Oral: onset is 1-2 hours after administration. |
| Duration of Action | Duration of action is approximately 24 hours, allowing for once-daily dosing. |
| Molecular Weight | 288.42 |
ENPRESSE-21 (ethinyl estradiol/norethindrone acetate) is an oral contraceptive. One tablet (0.035 mg ethinyl estradiol/0.5 mg norethindrone acetate) by mouth once daily for 21 days, followed by 7 placebo days.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (GFR <30 mL/min) or dialysis; use is not recommended. |
| Liver impairment | Contraindicated in Child-Pugh Class A, B, or C due to impaired steroid metabolism. No dose adjustment defined; avoid use in any hepatic impairment. |
| Pediatric use | Not indicated for use before menarche. For post-menarche adolescents: same dosing as adults (0.035 mg ethinyl estradiol/0.5 mg norethindrone acetate once daily for 21 days). |
| Geriatric use | Not indicated for use in elderly women; no menopausal indication. No dose adjustment studied; use is not recommended. |
| 1st trimester | Category D; may cause fetal harm; avoid unless benefit justifies risk. |
| 2nd trimester | Category D; use only if clearly needed; consider risk of fetal masculinization. |
| 3rd trimester | Contraindicated; virilization of female fetus, risk of fetal abnormalities. |
Clinical note
Comprehensive clinical and safety monograph for ENPRESSE-21 (ENPRESSE-21).
| Placental transfer | Crosses placenta; documented transfer. |
| Breastfeeding | Excreted in human milk; may cause adverse effects in nursing infants; use is contraindicated during breastfeeding. |
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | First trimester: Increased risk of neural tube defects (NTDs) due to folate antagonism; highest risk between days 17-56 post-conception. Second trimester: Risk of intrauterine growth restriction (IUGR) and preterm birth. Third trimester: Potential for neonatal folate deficiency and hematopoietic suppression. |
| Fetal Monitoring | Monitor maternal folate levels monthly; perform fetal ultrasound at 18-20 weeks for neural tube defects; assess fetal growth in third trimester; neonatal evaluation for folate deficiency at birth. |
| Fertility Effects | May reduce ovulation in women due to antifolate effects; men may experience decreased spermatogenesis; discontinue at least 3 months prior to conception attempts. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use this product.
| Serious Effects |
PregnancyBreastfeedingKnown hypersensitivity to norethindroneUndiagnosed abnormal genital bleedingKnown or suspected breast cancerActive thromboembolic disorders
| Precautions | Cardiovascular events (thrombosis, stroke, MI); liver disease; hypertension; gallbladder disease; carbohydrate/lipid effects; headache; irregular bleeding; depression; fluid retention; hyperkalemia (drospirenone has antimineralocorticoid activity); potential for decreased efficacy with hepatic enzyme inducers. |
| Food/Dietary | Avoid high-potassium foods (bananas, oranges, spinach, potatoes, tomatoes) and potassium-containing salt substitutes. Grapefruit juice may increase spironolactone levels; avoid concurrent consumption. Caffeine may antagonize diuretic effect. Alcohol exacerbates hypotension and dizziness. |
| Clinical Pearls | ENPRESSE-21 is a spironolactone/hydrochlorothiazide combination. Monitor serum potassium and renal function within 1 week of initiation, especially in elderly or diabetic patients. Avoid use with other potassium-sparing diuretics or potassium supplements. Titrate dose to blood pressure response; maximal antihypertensive effect may take 2-4 weeks. Caution in patients with hepatic impairment due to risk of fluid and electrolyte imbalances. |
| Patient Advice | Take exactly as prescribed, usually once daily in the morning to avoid nighttime urination. · Avoid potassium-rich foods (bananas, oranges, potatoes) and salt substitutes containing potassium. · Report muscle cramps, irregular heartbeat, dizziness, or excessive thirst immediately. · Limit alcohol intake as it may increase dizziness or hypotension. · Do not discontinue abruptly; taper under medical supervision to avoid rebound hypertension. |
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