COMBIPATCH
Clinical safety rating: caution
Comprehensive clinical and safety monograph for COMBIPATCH (COMBIPATCH).
Combipatch contains estradiol, an estrogen, and norethindrone acetate, a progestin. Estrogens bind to estrogen receptors, leading to gene transcription and physiological effects. Norethindrone acetate transforms proliferative endometrium into secretory endometrium, reducing endometrial hyperplasia risk.
| Metabolism | Estradiol is metabolized primarily in the liver via hydroxylation by CYP450 enzymes (extensively) and conjugation to glucuronides and sulfates. Norethindrone acetate is deacetylated to norethindrone, which is metabolized by reduction and sulfate conjugation; CYP450-mediated oxidation is a minor pathway. |
| Excretion | Estradiol: 90% renal as glucuronide and sulfate conjugates, 10% biliary/fecal. Norethindrone: 60% renal, 40% biliary/fecal. |
| Half-life | Estradiol: 12-16 hours terminal half-life. Norethindrone: 8-10 hours. Steady-state reached by day 3-5. |
| Protein binding | Estradiol: 98-99% bound to SHBG and albumin. Norethindrone: 95-98% bound to SHBG and albumin. |
| Volume of Distribution | Estradiol: 1.2-1.6 L/kg. Norethindrone: 4-6 L/kg. Indicates extensive tissue distribution. |
| Bioavailability | Transdermal: Estradiol 100% (avoid first-pass). Oral estradiol: 2-10% (not applicable for Combipatch). Norethindrone: transdermal 100%. |
| Onset of Action | Transdermal: Estradiol levels increase within 2-4 hours; clinical effect on vasomotor symptoms within 2-4 weeks. |
| Duration of Action | Transdermal patch provides continuous delivery over 7 days; sustained hormone levels for 7 days. Clinical duration for symptom relief persists as long as patch applied. |
| Molecular Weight | Estradiol: 272.38 Da; Norethindrone: 298.42 Da |
Transdermal: One patch applied twice weekly (every 3-4 days). Each patch delivers estradiol 0.05 mg/day and norethindrone acetate 0.14 mg/day or 0.05/0.25 mg/day.
| Dosage form | FILM, EXTENDED RELEASE |
| Renal impairment | No dose adjustment necessary for mild to moderate renal impairment. Not studied in severe renal impairment (GFR <30 mL/min); use with caution. |
| Liver impairment | Contraindicated in patients with known or suspected liver disease, including hepatic impairment Child-Pugh class B or C. Use not recommended in any degree of hepatic impairment. |
| Pediatric use | Safety and efficacy have not been established in pediatric patients. Not indicated for use in children. |
| Geriatric use | No specific dose adjustment recommended based on age alone; use lowest effective dose for shortest duration due to increased risks of thromboembolism, stroke, dementia, and breast cancer in women over 65. |
| 1st trimester | Combipatch (estradiol/norethindrone) is contraindicated in pregnancy. Use is not recommended due to risk of fetal harm, including urogenital abnormalities and potential carcinogenic effects. |
| 2nd trimester | Combipatch is contraindicated in pregnancy. Estrogens can cause fetal harm, including reproductive tract abnormalities and potential long-term effects. |
| 3rd trimester | Combipatch is contraindicated in pregnancy. Estrogens may cause delayed parturition and fetal complications. Norethindrone may cause masculinization of female fetuses. |
Clinical note
Comprehensive clinical and safety monograph for COMBIPATCH (COMBIPATCH).
| Placental transfer | Estradiol and norethindrone cross the placenta. Estradiol is transferred readily; norethindrone is also detected in fetal circulation. |
| Breastfeeding | Estradiol and norethindrone are excreted in breast milk. Use during breastfeeding is not recommended as it may reduce milk production and quality, and expose the infant to hormones. Alternative methods should be considered. |
■ FDA Black Box Warning
Estrogens plus progestin therapy should not be used for the prevention of cardiovascular disease or dementia. Increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis have been reported. Estrogen plus progestin therapy has been shown to increase the risk of probable dementia in postmenopausal women.
| Serious Effects |
Pregnancy or suspected pregnancyUndiagnosed abnormal genital bleedingKnown or suspected breast cancerKnown or suspected estrogen-dependent neoplasiaActive or past history of venous thromboembolism (VTE)Active or recent arterial thromboembolic disease (e.g., stroke, MI)Known protein C, protein S, or antithrombin deficiency or other thrombophilic disordersLiver disease or impaired liver functionHypersensitivity to any component of Combipatch
| Precautions | Cardiovascular disorders: Increased risk of stroke, DVT, pulmonary embolism, and myocardial infarction, especially in women >35 years who smoke., Malignant neoplasms: Increased risk of endometrial cancer (unopposed estrogen), breast cancer (with progestin), and ovarian cancer., Dementia: Increased risk of probable dementia in women ≥65 years., Gallbladder disease: Increased risk., Hypertriglyceridemia: Possible pancreatitis., Fluid retention: Caution in cardiac or renal dysfunction., Hypocalcemia and hypo- and hyperthyroidism: Monitor., Hepatic hemangiomas: Enlargement possible. |
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| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | First trimester: Epidemiological studies suggest a small increased risk of congenital anomalies, particularly cardiac defects and hypospadias, with estrogen-progestin combinations. Second and third trimesters: Fetal exposure to estrogens may cause adverse effects including urogenital abnormalities and possibly neurodevelopmental effects. Combipatch is not indicated for use in pregnancy and should be discontinued if pregnancy occurs. |
| Fetal Monitoring | If inadvertently used during pregnancy, monitor fetal development with ultrasound to assess for congenital anomalies. No routine monitoring is required as Combipatch is contraindicated in pregnancy. |
| Fertility Effects | Estrogen-progestin combinations can suppress ovulation and delay return to fertility after discontinuation. Contraceptive use, including Combipatch, may mask early pregnancy. Upon discontinuation, return to fertility typically occurs within one to two menstrual cycles. |
| Food/Dietary | Grapefruit juice may increase systemic exposure to estradiol; avoid excessive consumption. No other significant food interactions are reported. Maintain a diet consistent with managing cardiovascular risk factors (low sodium, low saturated fat) as hormone therapy may increase risk of thromboembolism. |
| Clinical Pearls | Combipatch is a combination of estradiol and norethindrone acetate, indicated for menopausal hormone therapy in women with an intact uterus. Do not use in women with a uterus for estrogen-only therapy due to increased risk of endometrial cancer. Apply to clean, dry, non-irritated skin on the lower abdomen, avoiding the waistline and breasts. Rotate application sites with at least a 1-week interval between applications to the same site. Monitor for signs of thromboembolism, stroke, or breast cancer. Discontinue if jaundice or visual disturbances occur. Dose reductions may be needed in hepatic impairment. |
| Patient Advice | Apply the patch to clean, dry, hairless skin on the lower abdomen; do not apply to breasts or waistline. · Change the patch twice weekly (every 3-4 days) and rotate application sites to prevent skin irritation. · If a patch falls off, reapply a new patch and continue the same schedule; do not reapply the same patch. · Do not smoke while using this medication, as smoking increases the risk of serious cardiovascular side effects. · Report any symptoms of blood clots (e.g., leg pain, swelling, chest pain, sudden shortness of breath) immediately. · You may experience breast tenderness, nausea, or vaginal bleeding; notify your healthcare provider if these persist. · This medication does not protect against sexually transmitted infections or HIV. · Store patches at room temperature away from heat and moisture. |