Mifepristone

Pronunciation: mi-FE-pri-stone
Class: Abortifacient

Trade Names

Mifeprex
- Tablets 200 mg

Pharmacology

Competes with progesterone at progesterone-receptor sites.

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Pharmacokinetics

Absorption

Rapidly absorbed. T max is approximately 90 min, C max is 1.98 mg/L, and absolute bioavailability (20 mg oral) is 69%.

Distribution

Mifepristone is 98% protein bound and displays nonlinear kinetics.

Metabolism

Metabolized via pathways involving N-demethylation and terminal hydroxylation of the 17-propynyl chain. In vitro, CYP-450 3A4 is primarily responsible for metabolism. Major metabolite is N-monodemethyated metabolite.

Elimination

83% is excreted in feces and 9% in urine. Elimination is slow at first (50% eliminated in 12 to 72 h) and then becomes more rapid with t ½ of 18 h. Serum levels are undetectable by 11 days.

Indications and Usage

Termination of intrauterine pregnancy through day 49 of pregnancy.

Unlabeled Uses

Emergency contraception; uterine leiomyomata.

Contraindications

Confirmed or suspected ectopic pregnancy or undiagnosed adnexal mass; intrauterine device in place; chronic adrenal failure; concurrent long-term corticosteroid therapy; history of allergy to mifepristone, misoprostol, or other prostaglandin; hemorrhagic disorders or concurrent anticoagulant therapy; inherited porphyrias.

Dosage and Administration

Patients must read the Medication Guide and read and sign the Patient Agreement prior to administering mifepristone.

Adult Day 1

PO Mifepristone 600 mg in a single dose.

Day 3

PO Unless a confirmed abortion has occurred, administer misoprostol 400 mcg.

Day 14

PO Follow-up visit to confirm by clinical examination or ultrasonographic scan that a complete termination of pregnancy has occurred.

Storage/Stability

Store tablets at controlled room temperature (59° to 86°F).

Drug Interactions

Erythromycin, grapefruit juice, itraconazole, ketoconazole

May increase mifepristone plasma levels by inhibiting mifepristone CYP3A4 metabolism.

Carbamazepine, dexamethasone, phenobarbital, phenytoin, rifampin, St. John's wort

May decrease mifepristone plasma levels by inducing mifepristone CYP metabolism.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Syncope (1%).

CNS

Headache (31%); dizziness (12%); fatigue (10%); insomnia (3%); anxiety, asthenia, fainting (2%).

GI

Abdominal pain (96%); nausea (61%); vomiting (26%); diarrhea (20%); dyspepsia (3%).

Genitourinary

Uterine cramping (83%); uterine hemorrhage (5%); vaginitis (3%); leucorrhea, pelvic pain (2%); endometritis/salpingitis/pelvic inflammatory disease (1%).

Hematologic-Lymphatic

Decreased hemoglobin (6%); anemia (2%).

Musculoskeletal

Back pain (9%); rigors (3%); leg pain (2%).

Respiratory

Sinusitis (2%).

Miscellaneous

Fever, viral infections (4%).

Precautions

Warnings

Serious and sometimes fatal infections and bleeding occur very rarely following spontaneous, surgical, and medical abortions, including following mifepristone use. Prior to prescribing, inform patient about risk of these serious events and discuss the Medication Guide and the Patient Agreement. Ensure patient knows whom to call and what to do, including going to an emergency room if none of the provided contacts are reachable, if she experiences sustained fever, severe abdominal pain, prolonged heavy bleeding, or syncope.

Patients with serious bacterial infections and sepsis can present without fever, bacteremia or significant findings on pelvic examination following abortion. A high index of suspicion is needed to rule out sepsis.

Prolonged heavy bleeding may be a sign of incomplete abortion or other complications and prompt medical or surgical intervention may be needed. Advise patients to seek immediate medical attention if they experience prolonged heavy vaginal bleeding.

Advise patients to take their Medication Guide with them if they visit an emergency room or another health care provider who did not prescribe mifepristone, so that provider will be aware that patient is undergoing a medical abortion.


Monitor

Qualified health care provider must supervise administration. Clinical examination is necessary to confirm complete termination of pregnancy 14 days after mifepristone administration.

Emergency treatment

Adequate access to medical facilities equipped to provide emergency treatment of incomplete abortion, blood transfusions, and emergency resuscitation must be assured during period from first visit until discharged by health care provider.


Pregnancy

Indicated for termination of pregnancy.

Lactation

Undetermined.

Children

Safety and efficacy not established.

Special Risk Patients

Treat women older than 35 yr of age who smoke 10 or more cigarettes/day with caution.

Availability

Available only through selected health care provider offices.

Infection and sepsis

Serious bacterial infections, including very rare cases of fatal septic shock, have occurred. Sustained fever of 100.4°F or higher, severe abdominal pain, or pelvic tenderness may be an indication of infection.

Vaginal bleeding

Occurs in almost all patients.

Overdosage

Symptoms

Adrenal failure.

Patient Information

  • Explain name, action, and potential side effects of drug, including risk of fetal malformation if the treatment fails.
  • Give patient a copy of Medication Guide and signed Patient Agreement. Advise patient to take Medication Guide with them if they visit an emergency room or another health care provider who did not prescribe mifepristone.
  • Review treatment regimen, including potential need to use misoprostol if abortion has not occurred within 2 days of taking mifepristone and need for follow-up examination about 14 days after taking mifepristone to confirm complete termination of pregnancy.
  • Provide patient with instructions on whom to call, including phone number and what to do in the event of an emergency following administration of both mifepristone and misoprostol.
  • Inform patient that vaginal bleeding and uterine cramping will probably occur, especially after taking misoprostol, and that bleeding and spotting usually lasts for 9 to 16 days but could last longer. Advise patient to immediately notify health care provider using supplied phone number if they experience severe abdominal pain, fever of 100.4° F or higher that lasts for more than 4 h, or excessive vaginal bleeding (eg, soak through 2 thick full-size sanitary pads per hour for 2 consecutive h).
  • Advise patient that nausea, headache, dizziness, extreme tiredness, or back pain also can occur as a result of therapy. Contact health care provider if any of these occur and are intolerable.
  • Advise patient that another pregnancy could occur following termination of this pregnancy and before return of normal menses. Advise patient that contraception can be started as soon as termination of this pregnancy has been confirmed or before resuming sexual intercourse.

Copyright © 2009 Wolters Kluwer Health.

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