Etonogestrel

Trade Names:Implanon- Implant 68 mg

Pharmacology

Suppresses ovulation, increases viscosity of the cervical mucus, and alters the endometrium.

Pharmacokinetics

Absorption

Bioavailability is approximately 100%. Mean C _max ranges from 781 to 894 pg/mL and is reached within a few weeks after insertion. Concentration decreases gradually over time to 156 to 177 pg/mL at 36 mo.

Distribution

Vd averages 201 L. 66% bound to plasma albumin.

Metabolism

Etonogestrel is metabolized in the liver by CYP3A4.

Elimination

Elimination t _½ is approximately 25 h. Etonogestrel is excreted mainly in the urine as conjugates. After removal of the implant, concentrations decrease below assay sensitivity by 1 wk.

Indications and Usage

Prevention of pregnancy.

Unlabeled Uses

Male contraceptive agent.

Contraindications

Known or suspected pregnancy; current or past history of thrombosis or thromboembolic disorders; hepatic tumors or active liver disease; undiagnosed abnormal genital bleeding; known or suspected carcinoma of the breast or personal history of breast cancer; hypersensitivity to any component of the product.

Dosage and Administration

Subdermal implant Insertion and removal of the etonogestrel implant are performed by a health care provider. The implant contains etonogestrel 68 mg and provides reversible contraception for up to 3 yr.

General Advice

• Rule out pregnancy before inserting the etonogestrel implant.
• Insert etonogestrel so that it is palpable.

Storage/Stability

Store at 59° to 86°F. Protect from light.

Drug Interactions

Breakthrough bleeding or unintended pregnancy may occur. Consider use of an additional nonhormonal contraceptive method.

Plasma hormone levels may be increased.

Safety and efficacy of oral contraceptives may be affected.

Laboratory Test Interactions

Sex hormone–binding globulin may be decreased for the first 6 mo after etonogestrel insertion, followed by gradual recovery; initially, thyroxine concentrations may be decreased slightly, followed by gradual recovery.

Adverse Reactions

Cardiovascular

Hypertension, migraine, varicose vein (less than 5%).

CNS

Headache (25%); dizziness (7%); depression, emotional lability, nervousness (6%); abnormal crying, anxiety, asthenia, decreased libido, fatigue, hypoesthesia, insomnia, somnolence (less than 5%).

Dermatologic

Acne (14%); pruritus, rash (less than 5%).

EENT

Pharyngitis (10%); abnormal vision, otitis media, rhinitis (less than 5%).

GI

Abdominal pain (11%); nausea (6%); anorexia, constipation, diarrhea, dyspepsia, flatulence, gastritis, vomiting (less than 5%).

Genitourinary

Vaginitis (14%); breast pain (13%); leukorrhea (10%); dysmenorrhea (7%); abnormal sexual function, breast discharge, breast enlargement, breast fibroadenosis, dysuria, genital pruritus, nonpuerperal lactation, ovarian cyst, pelvic cramping, positive cervical smear test, premenstrual cramping, vaginal discomfort (less than 5%).

Hematologic-Lymphatic

Bleeding irregularities (11%).

Local

Injection-site reaction, insertion-site pain (5%).

Metabolic-Nutritional

Increased weight (14%); decreased weight (less than 5%).

Musculoskeletal

Back pain (7%); arthralgia, myalgia, skeletal pain (less than 5%).

Respiratory

Upper respiratory tract infection (13%); sinusitis (6%); asthma, coughing (less than 5%).

Miscellaneous

Influenza-like symptoms (8%); pain (6%); allergic reaction, edema, fever, generalized edema, hot flushes, increased appetite (less than 5%).

Precautions

Pregnancy

Not indicated for use during pregnancy.

Lactation

Small amounts excreted in breast milk. May be used during lactation after postpartum wk 4.

Children

Safety and efficacy not established.

Hepatic Function

Etonogestrel may be metabolized poorly. If jaundice develops, etonogestrel may be poorly metabolized.

Bleeding irregularities

Changes in vaginal bleeding pattern may occur.

Contact lenses

Consider ophthalmologic examination in contact lens wearers who develop visual changes or lens intolerance.

Carcinoma of the breast

Women with breast cancer should not use hormonal contraceptives because breast cancer may be hormonally sensitive.

Depression

Carefully observe patients with a history of depression. If patients become severely depressed, consider removing the implant.

Ectopic pregnancy

Be alert for ectopic pregnancy after insertion.

Fluid retention

Because steroid contraceptives cause some degree of fluid retention, use them with caution in patients with conditions that may be aggravated by fluid retention.

Gallbladder disease

The risk of gallbladder disease may be increased slightly.

Hepatic neoplasm

Benign hepatic adenomas have been associated with use of combined oral contraceptives.

Hypertension

Incidence of hypertension increases with increasing doses of progestin.

Metabolic effects

Mild insulin resistance and small changes in glucose concentrations may occur.

Ovarian cysts

Atresia of the follicle may be delayed and follicle may continue to grow beyond the size attained in a normal cycle.

Smoking

Cigarette smoking increases the risk of serious CVP adverse reactions from use of combined hormonal contraceptives. It is not known if a similar risk exists with progestin-only methods.

Thrombosis

Serious thromboembolic reactions have been reported, including cases of fatal pulmonary emboli.

Patient Information

• Provide patient with a copy of the patient information leaflet and ensure she understands the information before etonogestrel insertion or removal.
• Inform patient that etonogestrel implant does not protect against HIV infection or other STDs.

Copyright © 2009 Wolters Kluwer Health.