Action

Unclear. Mirena may enhance local contraceptive efficacy by thickening the cervical mucus (which prevents passage of sperm into uterus), inhibiting sperm capacitation or survival, and altering the endometrium. Plan B is thought to prevent ovulation or fertilization.

Availability

Intrauterine system (Mirena): 52 mg levonorgestrel

Tablets (Plan B): 1.5 mg

Indications and dosages

➣ Intrauterine contraception for up to 5 years; heavy menstrual bleeding for women who choose to use intrauterine contraception

Adults: One intrauterine system (Mirena) inserted into uterus for up to 5 years

➣ Emergency contraception to prevent pregnancy

Adults: 1.5 mg (Plan B) P.O. as soon as possible within 72 hours after unprotected intercourse

Contraindications

Mirena-

• Hypersensitivity to drug or its components

• Known or suspected pregnancy

• Congenital or acquired uterine anomaly

• Acute pelvic inflammatory disease (PID) or history of PID (unless patient had subsequent intrauterine pregnancy)

• Postpartum endometritis or infected abortion within past 3 months

• Known or suspected uterine or cervical neoplasia or unresolved abnormal Papanicolaou (Pap) test

• Untreated acute cervicitis or vaginitis

• Acute hepatic disease or hepatic tumor (benign or malignant)

• Genital bleeding of unknown cause

• Conditions associated with increased risk of infection

• Genital actinomycosis

• Previously inserted intrauterine device that has not been removed

• Known or suspected breast cancer

• History of ectopic pregnancy or conditions that predispose to it

Plan B -

• Hypersensitivity to drug or its components

• Known or suspected pregnancy

• Undiagnosed abnormal genital bleeding

Precautions

Use Mirena cautiously in:

• diabetes mellitus

• breastfeeding patients.

Use Plan B cautiously in:

• coagulopathy

• diabetes mellitus

• patients receiving anticoagulants concurrently.

Administration

• Know that Mirena should be inserted under aseptic conditions by health care professional familiar with procedure.

• Verify that patient isn't pregnant before Mirena insertion.

• Know that Plan B should be given as soon as possible within 72 hours of unprotected sexual intercourse. Drug isn't suitable as long-term contraceptive.

Adverse reactions

CNS: headache (Mirena, Plan B), fatigue, dizziness (Plan B), severe headache, migraine, nervousness, depression (Mirena)

CV: hypertension (Mirena)

EENT: sinusitis (Mirena)

GI: nausea, vomiting, abdominal pain (Mirena, Plan B), diarrhea (Plan B), intestinal perforation or obstruction (Mirena)

GU: breast tenderness (Mirena, Plan B); lighter or heavier menstrual bleeding (Plan B); breast pain; increased progesterone levels; ovarian cysts; dysmenorrhea; amenorrhea; spotting; erratic or prolonged menstrual bleeding; pelvic infection; vaginitis; cervicitis; dyspareunia; leukorrhea; decreased libido; abnormal Pap smear; expulsion, embedment in myometrium, adhesions, cervical or ureteral perforation (Mirena)

Hematologic: anemia (Mirena)

Hepatic: jaundice (Mirena)

Musculoskeletal: back pain (Mirena)

Respiratory: upper respiratory tract infection (Mirena)

Skin: skin disorder, acne, eczema, hair loss (Mirena)

Other: water retention, weight gain, sepsis (Mirena)

Interactions

Drug-drug. Hepatic enzyme-inducing drugs (such as barbiturates, carbamazepine, phenytoin, rifampin): decreased Plan B efficacy

Drug-diagnostic tests. Glucose: altered level (Mirena)

Patient monitoring

• Monitor blood pressure.

• Watch for adverse reactions, especially changes in menstrual bleeding.

• Monitor blood glucose level in diabetic patients.

• Check liver function tests frequently.

Patient teaching

• Tell patient taking either product that drug does not prevent HIV or other sexually transmitted diseases.

• Teach patient using Mirena how to check (after menstrual period) to make sure thread still protrudes from cervix. Caution her not to pull on thread, because this could cause displacement.

See Instruct patient using Mirena to immediately report fever, chills, unusual vaginal discharge, or abdominal or pelvic pain or tenderness.

• Explain that for maximum efficacy, patient should take Plan B as soon as possible after unprotected sex.

• Inform patient that Plan B isn't intended for routine contraception and doesn't terminate existing pregnancy.

• Tell patient to report adverse reactions.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.