NORPLANT SYSTEM IN PLASTIC CONTAINER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NORPLANT SYSTEM IN PLASTIC CONTAINER (NORPLANT SYSTEM IN PLASTIC CONTAINER).
Levonorgestrel is a synthetic progestogen that inhibits ovulation, thickens cervical mucus to impede sperm penetration, and alters endometrial receptivity to implantation.
| Metabolism | Primarily metabolized in the liver via cytochrome P450 (CYP3A4) to inactive metabolites. |
| Excretion | Renal (40-60% as metabolites), Fecal (25-35% as metabolites), Biliary (minor). Levonorgestrel is extensively metabolized; <5% excreted unchanged. |
| Half-life | Terminal elimination half-life: 16-18 hours after single dose; during steady-state (implant), effective half-life is extended to 2-3 weeks due to continued release from the implant. |
| Protein binding | 98-99% bound, primarily to sex hormone-binding globulin (SHBG) and albumin; distribution affected by SHBG levels. |
| Volume of Distribution | Approximately 1.8 L/kg (range 1.5-2.0 L/kg); indicates extensive tissue distribution (e.g., fat, muscle) and binding to plasma proteins. |
| Bioavailability | Subdermal implant: 100% (systemic, as drug is released directly into circulation). Oral (tablet): approximately 90% but subject to first-pass metabolism. |
| Onset of Action | Subdermal implant: Contraceptive effect achieved within 24 hours of insertion if placed during first 5 days of menstrual cycle; within 24 hours if inserted immediately postpartum. |
| Duration of Action | Contraceptive efficacy for up to 5 years after insertion; return of fertility delayed; ovulation resumes within 3-6 months after removal. |
Subdermal implantation of 6 capsules (each containing 36 mg levonorgestrel) in the upper arm, providing contraception for up to 5 years.
| Dosage form | IMPLANT |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (eGFR >30 mL/min/1.73 m²). Insufficient data for severe impairment (eGFR <30 mL/min/1.73 m²); use with caution due to potential for decreased clearance and increased exposure. |
| Liver impairment | Contraindicated in patients with acute or chronic liver disease, including Child-Pugh class B or C. No dose adjustment is applicable; alternative contraception should be considered. |
| Pediatric use | Approved for postmenarcheal adolescents (<18 years) at the same adult dose: subdermal implantation of 6 capsules. Weight-based adjustments not required. |
| Geriatric use | Not typically used in elderly populations due to increased risk of thromboembolic events and declining renal/hepatic function. Consider alternative contraception for postmenopausal women over 45 years. No specific dose adjustment; use is generally not recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NORPLANT SYSTEM IN PLASTIC CONTAINER (NORPLANT SYSTEM IN PLASTIC CONTAINER).
| Breastfeeding | Etonogestrel is excreted in breast milk in small amounts. The M/P ratio is approximately 0.44. Based on available data, no adverse effects on infant growth or development have been observed. However, use during lactation is recommended only after the infant is at least 6 weeks old and if benefits outweigh risks. Milk production may be reduced, especially in early postpartum period. |
| Teratogenic Risk | FDA Pregnancy Category X. Contraindicated in pregnancy. Etonogestrel is released from the implant and can cause fetal harm. First trimester: Risk of congenital anomalies, including cardiovascular and limb defects, based on animal studies. Second and third trimesters: Potential for masculinization of female fetuses due to progestin exposure. Postnatal effects: Possible long-term neurobehavioral effects. Pregnancy should be ruled out before insertion and removed if pregnancy occurs. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Known or suspected pregnancy","Current or past thromboembolic disorders","Hepatic tumors (benign or malignant)","Active liver disease","Undiagnosed abnormal uterine bleeding","Hypersensitivity to levonorgestrel or any component of the system"]
| Precautions | ["Thrombotic disorders (e.g., thrombophlebitis, pulmonary embolism)","Hepatic disease (e.g., hepatic adenoma)","Ectopic pregnancy risk","Cervical cancer risk","Irregular bleeding patterns","Expulsion or migration of implants","Ovarian cysts","Increased risk of breast cancer"] |
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| Fetal Monitoring | Not applicable during pregnancy as contraindicated. Prior to insertion: Rule out pregnancy, perform complete medical history, blood pressure measurement, and exclude active liver disease or hormone-sensitive cancers. During use: Regular follow-up every 6-12 months; monitor for implant site complications, check for signs of thrombosis, liver dysfunction, or hypertension. If pregnancy occurs, remove implant immediately and monitor for ectopic pregnancy signs. |
| Fertility Effects | Reversible. Return to fertility occurs rapidly after removal; ovulation resumes within 3–4 weeks. No long-term impairment of fertility. No effect on future pregnancy outcomes. Use does not cause infertility after discontinuation. |