FEMINONE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FEMINONE (FEMINONE).
FEMINONE (progesterone) is a steroid hormone that binds to the progesterone receptor, modulating gene expression in target tissues. It transforms the endometrium from proliferative to secretory phase, reduces endometrial hyperplasia risk, and suppresses gonadotropin release via negative feedback.
| Metabolism | Primarily hepatic via CYP3A4-mediated hydroxylation and reduction, followed by conjugation with glucuronide and sulfate. Major metabolites include pregnanediols and pregnanolones. |
| Excretion | Feminone (norethindrone) is primarily excreted in urine (approximately 70-80% as metabolites, with <5% as unchanged drug) and feces (20-30%). |
| Half-life | Terminal elimination half-life is approximately 7-8 hours (range 5-12 h); clinical significance: steady-state reaches after ~2-3 days, necessitates daily dosing for contraceptive efficacy. |
| Protein binding | Approximately 97% bound to serum albumin (primarily) and sex hormone-binding globulin (SHBG). |
| Volume of Distribution | Vd ~4 L/kg (range 3-5 L/kg); indicates extensive extravascular distribution and tissue binding. |
| Bioavailability | Oral bioavailability is approximately 65% (range 50-80%) due to first-pass metabolism. |
| Onset of Action | Oral: Onset of contraceptive effect after 7 days of continuous dosing (if started on day 1 of menstrual cycle); immediate if started within first 5 days. Subdermal implant (not Feminone but similar progestin): onset within 24 hours. |
| Duration of Action | Oral: Duration of contraceptive effect is 24 hours with daily dosing; missed pill >3 hours requires backup contraception. Clinical note: duration of endometrial effects lasts beyond dosing interval. |
0.625 mg orally once daily
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR >30 mL/min; use with caution in GFR <30 mL/min due to limited data |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated |
| Pediatric use | Not approved for use in pediatric patients |
| Geriatric use | Start at 0.3 mg once daily; titrate to response with monitoring for adverse effects |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FEMINONE (FEMINONE).
| Breastfeeding | Excreted in breast milk; M/P ratio ~1.2. May reduce milk production (progestin effect). Avoid use during breastfeeding. Weigh risk vs benefit. |
| Teratogenic Risk | FEMINONE (norethisterone) is contraindicated in pregnancy. First trimester: exposure associated with masculinization of female fetus (clitoral enlargement, labial fusion) and cardiovascular defects. Second/third trimester: risk of masculinization persists; potential for DVT in mother. Pregnancy category X. |
| Fetal Monitoring |
■ FDA Black Box Warning
Cardiovascular disorders, myocardial infarction, stroke, pulmonary embolism, and deep vein thrombosis have been reported with estrogen-progestin therapy. Should not be used for prevention of cardiovascular disease or dementia.
| Serious Effects |
Known or suspected pregnancy, undiagnosed abnormal genital bleeding, known or suspected breast cancer, active deep vein thrombosis or pulmonary embolism, liver impairment or disease, history of thrombophlebitis or thromboembolic disorders.
| Precautions | Cardiovascular disorders, thromboembolic events, breast cancer risk, dementia risk, visual abnormalities, fluid retention, elevated blood pressure, hypercalcemia, glucose intolerance. |
| Food/Dietary | No significant food interactions known. Grapefruit juice does not affect progestin metabolism, in contrast to estrogens. However, high-fat meals may slightly reduce absorption; consistent administration with food or without food is recommended. |
Loading safety data…
| If exposure occurs: ultrasound for fetal anatomy (especially external genitalia); monitor for signs of thromboembolism in mother; assess liver function due to potential hepatotoxicity. |
| Fertility Effects | Suppresses ovulation (contraceptive effect). Chronic use may delay return to fertility (prolonged anovulation). No long-term impairment after discontinuation. |
| Clinical Pearls | FEMINONE is a progestogen-only pill (POP) used for contraception. Unlike combined oral contraceptives, it does not contain estrogen. Its contraceptive efficacy relies on thickening cervical mucus and inhibiting ovulation inconsistently. It must be taken at the same time every day (within a 3-hour window) for maximal effectiveness. In emergency contraception, a specific dosing regimen (ulipristal acetate) is not interchangeable with FEMINONE. It is safe for use during breastfeeding and in women with estrogen-sensitive conditions or cardiovascular risks. |
| Patient Advice | Take FEMINONE at exactly the same time every day; missed pills significantly reduce efficacy. · If you vomit within 3 hours of taking a pill, take another pill as soon as possible. · Use backup contraception (e.g., condoms) if you miss a pill or are more than 3 hours late. · FEMINONE does not protect against sexually transmitted infections. · Common side effects include irregular menstrual bleeding, headaches, nausea, and breast tenderness. · Consult your healthcare provider if you suspect pregnancy or experience severe lower abdominal pain (possible ectopic pregnancy). |