levonorgestrel implants Norplant System
Pharmacologic classification: progestin Therapeutic classification: contraceptive Pregnancy risk category X
Available forms Available by prescription only Implants: 36 mg in each of six Silastic capsules; kits also include trocar, scalpel, forceps, syringe, two needles, package of skin
closures, three packages of gauze sponges, stretch bandages, and surgical drape
Indications and dosages Long-term (up to 5 years) reversible prevention of pregnancy. Adults: Six Silastic capsules containing 36 mg each for a total of 216 mg are surgically implanted in the superficial plane beneath
the skin of a woman’s upper arm during first 7 days of onset of menses.
Pharmacodynamics Contraceptive action: Levonorgestrel is a synthetic, biologically active progestin that exhibits no significant estrogenic activity. A continuous
low dose of levonorgestrel is diffused through the wall of each capsule. Pregnancy is prevented by at least two mechanisms:
inhibition of ovulation and thickening of the cervical mucus.
Pharmacokinetics Absorption: 100% bioavailable. Plasma levels average 0.3 ng/ml over 5 years but are highly variable as a function of individual metabolism
and body weight. Distribution: Bound by the circulating protein sex hormone-binding globulin. Metabolism: Metabolized by the liver. Excretion: Metabolites are excreted in the urine.
Route |
Onset |
Peak |
Duration |
Subdermal |
24 hr |
24 hr |
Unknown |
|
Contraindications and precautions Contraindicated in patients with active thrombophlebitis or thromboembolic disorders, undiagnosed abnormal genital bleeding,
acute liver disease, malignant or benign liver tumors, known or suspected breast cancer, known or suspected pregnancy, history
of idiopathic intracranial hypertension, and hypersensitivity to levonorgestrel or components of the Norplant System. Use cautiously in diabetic and prediabetic patients and in those with history of depression or hyperlipidemia.
Interactions Drug-drug. Carbamazepine, phenytoin: Reduce efficacy of levonorgestrel. Patient should take additional precautions to avoid pregnancy.
Adverse reactions CNS: headache, nervousness, dizziness, depression, tingling, numbness. GI: nausea, abdominal discomfort, appetite change. GU: amenorrhea, many days of bleeding or prolonged bleeding, spotting, irregular onset of bleeding, frequent onset of bleeding,
scanty bleeding, cervicitis, vaginitis, leukorrhea. Metabolic: weight gain. Musculoskeletal: mastalgia, musculoskeletal pain. Skin: dermatitis, acne, hirsutism, hypertrichosis, alopecia, infection, transient pain, itching (at implant site). Other: adnexal enlargement, removal difficulty, breast discharge.
Effects on lab test results May decrease thyroxine levels. May increase T3 uptake.
Overdose and treatment Overdose can occur if more than six Silastic capsules are in situ, resulting in fluid retention with its associated effects
and uterine bleeding irregularities.
Special considerations ALERT Implant devices were discontinued by the manufacturer and are no longer being inserted. Counsel patient on other birth control
options once her implant has expired and has been removed. The total implanted dose is 216 mg. Capsules were implanted subdermal in the midportion of the inside of the upper arm, 8
to 10 cm above the elbow crease. Each capsule is 2.4 mm in diameter and 34 mm in length. Reexamine patient at least yearly; examinations should focus on implant site, blood pressure, breasts, abdominal and pelvic
organs (including cervical cytology), and related laboratory tests. Monitor patient for recurrent or abnormal vaginal bleeding. Monitor patient with strong family history of breast cancer for breast nodules.
Patient education Tell patient that altered bleeding patterns tend to become more regular after 9 to 12 months. Warn patient to report heavy bleeding. Advise patient that, when laboratory studies are ordered, she should inform all health care providers that levonorgestrel
implants are being used. Tell patient who takes phenytoin or carbamazepine that she may need to use additional contraceptive measures.
Reactions may be common, uncommon, life-threatening, or
COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use
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