NORPLANT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NORPLANT (NORPLANT).
Progestin (levonorgestrel) suppresses gonadotropin secretion, inhibiting ovulation, thickening cervical mucus, and altering endometrial lining to prevent implantation.
| Metabolism | Primarily metabolized by CYP3A4 to hydroxylated metabolites; undergoes glucuronidation and sulfation. |
| Excretion | Renal: 40-50% (as metabolites), Fecal: 40-50% (as metabolites). Biliary excretion contributes to fecal elimination. Less than 1% excreted unchanged. |
| Half-life | Terminal elimination half-life: approximately 24.4 hours (range 16-30 hours) for levonorgestrel. After removal of implants, levonorgestrel levels decline with a half-life of 18-20 hours, but contraceptive effect persists for 1-2 cycles due to tissue reservoir. |
| Protein binding | 99.5% bound, primarily to sex hormone-binding globulin (SHBG) (approx. 60%) and albumin (approx. 40%). |
| Volume of Distribution | 1.8 L/kg (range 1.5-2.0 L/kg). Indicates extensive tissue distribution and binding to SHBG. |
| Bioavailability | Subdermal: 100% (bypasses first-pass metabolism). Oral: approximately 80-90% (not applicable to Norplant, which is subdermal). |
| Onset of Action | Subdermal implantation: contraceptive effect within 24 hours if inserted during first 7 days of menstrual cycle; otherwise, within 7 days. Immediate ovulation suppression achieved. |
| Duration of Action | Contraceptive efficacy for up to 5 years after insertion of 6 capsules. Removal results in rapid return of fertility within 1-2 months. Pregnancy may occur within first cycle after removal. |
6 subdermal capsules (36 mg levonorgestrel total) implanted subdermally in the inner aspect of the upper arm, effective for up to 5 years.
| Dosage form | IMPLANT |
| Renal impairment | No dose adjustment required for any stage of chronic kidney disease; however, monitor for potential adverse effects due to altered drug clearance. |
| Liver impairment | Contraindicated in severe hepatic dysfunction (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), no specific dose adjustment available; use with caution. |
| Pediatric use | Not recommended for use in females under 18 years of age due to lack of safety and efficacy data in this population. |
| Geriatric use | Not indicated for use in postmenopausal women; no elderly-specific studies are available. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NORPLANT (NORPLANT).
| Breastfeeding | Etonogestrel is excreted in breast milk; M/P ratio approximately 0.6. Small amounts detected in milk, but no reported adverse effects in nursing infants. Consider if benefit outweighs risk; not recommended for immediate postpartum use due to potential effects on milk production and infant metabolism. |
| Teratogenic Risk | Category X: Contraindicated in pregnancy. First trimester: Risk of fetal harm from exposure to etonogestrel; no adequate studies; teratogenic effects not established but risk of congenital anomalies cannot be excluded. Second and third trimesters: No fetal risks known; however, use is contraindicated due to lack of need and potential hormonal effects on developing fetus. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination hormonal contraceptives. Norplant does not contain estrogen; however, smoking and age >35 years are contraindicated.
| Serious Effects |
["Known or suspected pregnancy","Active thrombophlebitis or thromboembolic disorders","Undiagnosed abnormal genital bleeding","Known or suspected breast carcinoma","Benign or malignant liver disease","Hypersensitivity to levonorgestrel or any component"]
| Precautions | ["Thrombotic disorders","Hepatic disease","Ectopic pregnancy risk","Ovarian cysts","Menstrual irregularities","Insertion site complications"] |
Loading safety data…
| Fetal Monitoring | Monitor pregnancy test prior to insertion to exclude pregnancy. If pregnancy occurs with Norplant in situ, manage based on clinical circumstances; remove implant if possible. No routine fetal monitoring required for Norplant itself, but monitor for ectopic pregnancy if pregnancy occurs with implant in place. |
| Fertility Effects | Reversible; rapid return to normal fertility after removal. Ovulation resumes within 3-4 weeks. No long-term impairment of fertility or increased risk of congenital anomalies in future pregnancies. |