Professional Information

Levonorgestrel

Pronouncation: (LEE-voe-nor-JESS-truhl)
Class: Contraceptive, Hormones

Trade Names:
Mirena
- Levonorgestrel-releasing intrauterine system T-shaped unit containing a reservoir of 52 mg levonorgestrel covered by a silicone membrane

Trade Names:
Norplant System
- Levonorgestrel implants (subdermal) Set of 6 capsules each containing 36 mg levonorgestrel

Pharmacology

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Compare with other drugs.

Synthetic, biologically active progestin that transforms proliferative endometrium into secretory endometrium and inhibits secretion of pituitary gonadotropins, preventing follicular maturation and ovulation.

Pharmacokinetics

Distribution

Unlike other oral contraceptives, plasma levels with the levonorgestrel-releasing intrauterine system do not display peaks and troughs. Primarily bound to proteins, mainly sex hormone–binding globulin.

Metabolism

Extensively metabolized to a large number of inactive metabolites.

Elimination

The t _½ is 17 h. Both the parent drug and its metabolites are primarily excreted in urine.

Indications and Usage

Prevention of pregnancy.

Contraindications

Subdermal implants

Active thrombophlebitis or thromboembolic disorders; undiagnosed abnormal genital bleeding; known or suspected pregnancy; acute liver disease; benign or malignant liver tumors; known or suspected breast carcinoma.

Intrauterine system

Pregnancy or suspicion of pregnancy; congenital or acquired uterine anomaly; acute pelvic inflammatory disease (PID) or history of PID unless there has been a subsequent intrauterine pregnancy; postpartum endometritis or infected abortion in past 3 mo; genital bleeding of unknown etiology; untreated acute cervicitis or vaginitis, including bacterial vaginosis or other lower genital tract infection until infection is controlled; woman or sexual partner with multiple sexual partners; conditions associated with increased susceptibility to infections with microorganisms (eg, leukemia, AIDS, IV drug use); genital actinomycosis; previously inserted IUD that has not been removed; known or suspected carcinoma of the breast; history of ectopic pregnancy or condition that would predispose to ectopic pregnancy; hypersensitivity to any component of this product.

Dosage and Administration

Intrauterine system
Adults

Insert into uterine cavity within 7 days of onset of menstruation or immediately after first trimester abortion. Replace every 5 yr.

Subdermal implants
Adults

6 capsules inserted in midportion of upper arm during first 7 days of onset of menses. Remove after 5 yr.

Adults

PO 1 tablet (0.75 mg) within 72 h after unprotected intercourse; second tablet (0.75 mg) 12 h after the first dose.

Drug Interactions

Carbamazepine

Reduced contraceptive efficacy.

Phenytoin

Reduced contraceptive efficacy.

Rifampin

Possible reduced contraceptive efficacy.

Laboratory Test Interactions

Endocrine tests may be affected. Sex hormone-binding globulin concentrations may be decreased; thyroxine concentrations may be slightly decreased and triiodothyronine uptake may be increased.

Adverse Reactions

Cardiovascular

Syncope, bradycardia, hypertension (intrauterine system).

CNS

Headache; nervousness; dizziness; decreased libido (intrauterine system).

Dermatologic

Dermatitis; acne; hirsutism; hypertrichosis; scalp hair loss; pain, itching, or infection near implant site.

GI

Nausea; change in appetite; abdominal discomfort.

Genitourinary

Prolonged, irregular, frequent, or scanty bleeding; spotting; amenorrhea; cervicitis; leukorrhea; vaginitis.

Metabolic

Weight gain.

Respiratory

Upper respiratory tract infection, sinusitis (intrauterine system).

Miscellaneous

Adnexal enlargement; mastalgia; breast discharge; implant removal difficulty; musculoskeletal pain.

Precautions

Pregnancy

Category X .

Lactation

Excreted in breast milk.

Children

Safety and efficacy before menarche not established.

Bleeding irregularities

Most women can expect variation in menstrual bleeding patterns.

Delayed follicular atresia

Follicle may grow beyond usual size and may resemble ovarian cyst.

Ectopic pregnancies

Have occurred, although relationship to drug is not established.

Intrauterine pregnancy

Risk of septic abortion, miscarriage, sepsis, premature labor, and premature delivery may be increased with the intrauterine system.

Ocular lesions

Retinal thrombosis has occurred with oral contraceptives; consider possibility in levonorgestrel users.

Perforation

Perforation of the uterus and cervix by the intrauterine system may occur.

Thromboembolic disorders

Remove capsules if thrombophlebitis or thromboembolic disease occurs. Consider removal in patients immobilized for prolonged periods.

Valvular/Congenital heart disease

Patients with certain types of valvular or congenital heart disease and surgically constructed systemic-pulmonary shunts are at increased risk of infective endocarditis, and use of the intrauterine system may represent a potential source of septic emboli.

Overdosage

Symptoms

Fluid retention, uterine bleeding irregularities.

Patient Information

Explain that contraceptive method will be effective for 5 yr; capsules should be removed after that period, but can be removed at any time; and that removal should be done by a health care provider trained in procedure.
Encourage low-fat, low-cholesterol diet.
Teach patient to identify and report signs of wound infection after insertion.
Instruct patient to notify health care provider if capsule falls out.
Instruct patient to report the following symptoms to health care provider: jaundice, fluid retention, depression, vision changes, abnormal bleeding, and weight gain.
Emphasize that missed menstrual period is not an accurate indicator of pregnancy.
Explain that menstrual irregularities are common, especially during first year of therapy.
Emphasize importance of keeping follow-up visits to evaluate effectiveness of contraceptive therapy.