ACTIVELLA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ACTIVELLA (ACTIVELLA).
Combination of estradiol, an estrogen, and norethindrone acetate, a progestin. Estrogens act by binding to nuclear estrogen receptors (ERα and ERβ), which then interact with estrogen response elements on DNA, leading to changes in gene expression that regulate growth, differentiation, and function of female reproductive tissues and other tissues. Norethindrone acetate is a progestin that induces secretory changes in the endometrium, reducing the risk of endometrial hyperplasia and carcinoma associated with unopposed estrogen therapy.
| Metabolism | Estradiol is metabolized primarily in the liver via CYP3A4 and other CYPs, as well as by 17β-hydroxysteroid dehydrogenase and sulfotransferases. Norethindrone acetate is metabolized in the liver, primarily via reduction and conjugation, with CYP3A4 involved in some oxidative metabolism. |
| Excretion | Estradiol is primarily excreted in urine (∼50%) as glucuronide and sulfate conjugates, with ∼30% excreted in feces via biliary elimination. Norethindrone is excreted mainly in urine (∼60%) as metabolites, with ∼40% in feces. |
| Half-life | Estradiol has a terminal half-life of approximately 12–14 hours following transdermal administration. Norethindrone has a terminal half-life of approximately 8–10 hours. The combined product achieves steady-state within 3–5 days. |
| Protein binding | Estradiol is ∼98% bound to sex hormone-binding globulin (SHBG) and albumin. Norethindrone is ∼95–97% bound to SHBG and albumin. |
| Volume of Distribution | Estradiol has an apparent volume of distribution (Vd) of approximately 1.2 L/kg, indicating extensive distribution into tissues. Norethindrone has a Vd of approximately 3–5 L/kg, indicating wide distribution. |
| Bioavailability | Transdermal estradiol has a bioavailability of approximately 10% relative to oral administration due to avoidance of first-pass metabolism. Oral norethindrone acetate has a bioavailability of approximately 50–60%. |
| Onset of Action | The onset of action for estrogenic effects (e.g., relief of vasomotor symptoms) is typically within 2–6 weeks of daily patch application. No immediate clinical effect is expected. |
| Duration of Action | With continuous weekly dosing, clinical effects are maintained throughout the dosing interval. The patch is worn continuously for 7 days, after which a new patch is applied. |
One tablet (1 mg estradiol + 0.5 mg norethindrone acetate) orally once daily, continuously.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (CrCl <30 mL/min); use contraindicated. |
| Liver impairment | Contraindicated in severe hepatic disease (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), use caution and monitor; no specific dose adjustment established. |
| Pediatric use | Not indicated for use in pediatric patients; safety and efficacy not established. |
| Geriatric use | Start with the lowest effective dose; monitor for thromboembolic events and cognitive effects. No specific dose adjustment required, but consider age-related renal and hepatic decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ACTIVELLA (ACTIVELLA).
| Breastfeeding | Estradiol and norethindrone acetate are excreted into breast milk. Estradiol M/P ratio approximately 0.5; norethindrone M/P ratio approximately 0.4. May reduce milk production and alter composition. Use during breastfeeding is not recommended. |
| Teratogenic Risk | Pregnancy Category X. Estrogen and progestin exposure during the first trimester is associated with congenital anomalies including cardiovascular and limb defects. Use during the second and third trimesters is contraindicated due to risk of fetal genital abnormalities and potential long-term neurodevelopmental effects. Avoid in pregnancy. |
■ FDA Black Box Warning
Estrogens increase the risk of endometrial cancer. There is an increased risk of cardiovascular events, breast cancer, and probable dementia with estrogen plus progestin therapy. Actively monitor for these events.
| Serious Effects |
["Undiagnosed abnormal genital bleeding","Known, suspected, or history of breast cancer","Known or suspected estrogen-dependent neoplasia","Active or past history of venous thromboembolism (VTE) or arterial thromboembolism (ATE)","Current or recent (within 1 year) VTE or ATE","Known thrombophilic disorders (e.g., protein C, S, or antithrombin deficiency; factor V Leiden mutation)","Active or past history of arterial thromboembolic disease (e.g., stroke, MI)","Known liver impairment or disease","Known or suspected pregnancy","Hypersensitivity to any component of the product"]
| Precautions | ["Cardiovascular disorders: Increased risks of stroke, myocardial infarction, and venous thromboembolism (VTE).","Malignancy: Increased risk of breast cancer, endometrial cancer, and ovarian cancer.","Probable dementia: Increased risk in women aged 65 years or older.","Gallbladder disease, hypertriglyceridemia, fluid retention, hypocalcemia, and hereditary angioedema.","Retinal thrombosis: Discontinue if sudden vision loss occurs.","Laboratory tests: May alter thyroid function tests, coagulation tests, and glucose tolerance."] |
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| Fetal Monitoring | Not applicable as drug is contraindicated in pregnancy. If inadvertent exposure, monitor fetal growth, amniotic fluid index, and perform detailed anatomical ultrasound. |
| Fertility Effects | May inhibit ovulation at higher doses. In women using hormone therapy, endometrial proliferation may affect implantation. Fertility returns after discontinuation. No permanent adverse effects. |
| Food/Dietary | Grapefruit juice may increase estrogen levels by inhibiting CYP3A4; avoid excessive consumption. High-fat meals can increase absorption of oral estrogens; take consistently with or without food to maintain steady levels. |
| Clinical Pearls | For patients with an intact uterus, estrogen must be combined with a progestogen (norethindrone acetate) to prevent endometrial hyperplasia. Initiate at the lowest effective dose for the shortest duration. Avoid in women with active thromboembolic disease, known or suspected breast cancer, or undiagnosed abnormal genital bleeding. Consider transdermal route if oral absorption is compromised or for migraine with aura. |
| Patient Advice | Take this medication exactly as prescribed; do not skip doses or stop without consulting your doctor. · Report any unusual vaginal bleeding, breast lumps, or symptoms of blood clots (e.g., leg pain, chest pain, sudden shortness of breath, vision changes) immediately. · Smoking increases the risk of cardiovascular side effects, especially in women over 35; avoid smoking while on this therapy. · This medication does not protect against sexually transmitted infections or HIV. · Regular medical check-ups, including breast exams and mammograms, are essential during therapy. |