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Action/Kinetics:
Levonorgestrel implants are marketed either in a set of six flexible Silastic capsules each containing 36 mg of levonorgestrel (Norplant) or two rods containing 150 mg of levonorgestrel (Norgestrel II); an insertion kit is provided to the provider to assist with implantation. Small amounts of the drug slowly diffuse through the wall of each capsule resulting in blood levels of levonorgestrel that are lower than those seen when levonorgestrel or norgestrel is taken as oral contraceptive. The dose released is initially 85 mcg/day, followed by a decrease to approximately 50 mcg/day after 9 months, to 35 mcg/day after 18 months, and then leveling off to 30 mcg/day thereafter. Blood levels of levonorgestrel vary over a wide range and cannot be used as the sole measure of the risk of pregnancy. If used properly, the risk of pregnancy is less than 1 for every 100 users. Does not have any estrogenic effects. The implant system lasts up to 5 years and the contraceptive effect is rapidly reversed if the system is removed from the body.
Uses:
Prevention of pregnancy (system lasts for up to 5 years). A new system may be inserted after 5 years if continuing contraception is desired.
Contraindications:
Active thrombophlebitis, thromboembolic disorders, undiagnosed abnormal genital bleeding, acute liver disease, benign or malignant liver tumors, known or suspected breast carcinoma, confirmed or suspected pregnancy.
Special Concerns:
Menstrual bleeding irregularities are commonly observed. Monitor carefully women who have a family history of breast cancer or who have breast nodules. Monitor closely women being treated for hyperlipidemias because an increase in LDL levels may occur. Use with caution in individuals in whom fluid retention might be dangerous and in those with a history of depression. Do not insert until 6 weeks after parturition in women who are breast-feeding.
Side Effects:
Menstrual irregularities: Prolonged menses, spotting, irregular onset of menses, frequent menses, amenorrhea, scanty bleeding, cervicitis, vaginitis.
At implant site: Pain or itching, infection, bruising following insertion or removal, hyperpigmentation (reversible upon removal).
GI: Abdominal discomfort, nausea, change of appetite, weight gain.
CNS: Headache, nervousness, dizziness.
Dermatologic: Dermatitis, acne, hirsutism, scalp hair loss, excess hair growth.
Miscellaneous: Breast discharge, breast pain, leukorrhea, musculoskeletal pain, fluid retention, possibility of ectopic pregnancy in long-term users, delayed follicular atresia.
Laboratory Test Alterations:
Sex hormone binding globulin levels, T
4 levels (slight).
Uptake of T
3.
Overdose Management:
Symptoms: Overdosage can result if more than six capsules are inserted. Symptoms include fluid retention and uterine bleeding irregularities.
Treatment: All capsules should be removed.
Drug Interactions:
-
Carbamazepine /
Effectiveness
risk of pregnancy
-
Phenobarbital /
Effectiveness
risk of pregnancy
-
Phenytoin /
Effectiveness
risk of pregnancy
How Supplied:
Kit: 36 mg/implant, 150 mg/implant
Dosage
?Silastic Capsules, Rods
Six Silastic capsules (36 mg levonorgestrel each) or two rods (150 mg levonorgestrel each) implanted subdermally in the midportion of the upper arm (8-10 cm above the elbow crease). Capsules are distributed in a fan-like pattern 15° apart (total of 75°).
