Mifepristone

INTRODUCTION

Indications

Medical termination of intrauterine pregnancy up to day 49 of pregnancy.

Action

Antagonizes endometrial and myometrial effects of progesterone. Sensitizes the myometrium to contraction-inducing activity of prostaglandins. Therapeutic Effects: Termination of pregnancy.

Adverse Reactions/Side Effects

CNS: dizziness, fainting, headache, weakness. GI: abdominal pain, diarrhea, nausea, vomiting. GU: uterine bleeding, uterine cramping, ruptured ectopic pregnancy, pelvic pain.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Assess dizziness, fainting, and weakness that might affect gait, balance, and other functional activities (See Appendix C). Report persistent balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

Patient/Client-Related Instruction

• Instruct patient to notify health care professional immediately if she develops weakness, nausea, vomiting, diarrhea, with or without abdominal pain or fever more than 24 hr after taking mifepristone; may indicate life-threatening sepsis.

• Inform patient that vaginal bleeding and uterine cramping will probably occur. Bleeding or spotting occurs for an average of 9–16 days, but may continue for more than 30 days. Instruct patient to report any severe or unusual cramping, bleeding, or pelvic pain that extends beyond the expected time periods.

Pharmacokinetics

Absorption: Rapidly absorbed following oral administration (69% bioavailability).

Distribution: Unknown.

Protein Binding: 98%.

Metabolism and Excretion: Mostly metabolized by the liver (cytochrome CYP4503A4 [CY P4503A4] enzyme system).

Half-life: 18 hr.

Contraindications/Precautions

Contraindicated in: Presence of an intrauterine device (IUD); Confirmed or suspected ectopic pregnancy; Undiagnosed adnexal mass; Chronic adrenal failure; Concurrent long-term corticosteroid therapy; Bleeding disorders or concurrent anticoagulant therapy; Inherited porphyrias.

Use Cautiously in: Chronic medical conditions such as cardiovascular, hypertensive, hepatic, renal, or respiratory disease (safety and efficacy not established); Women >35 yrs old or who smoke ≥10 cigarettes/day.

Interactions

Drug-Drug: Blood levels and therapeutic effectiveness may be ↑ by ketoconazole, itraconazole, and erythromycin. Blood levels and effects may be ↓ by rifampin, dexamethasone, phenytoin, phenobarbital, and carbamazepine. Mifepristone may ↓ metabolism and ↑ effects of other drugs metabolized by the CYP4503A4 enzyme system, including some agents used during general anesthesia.

Drug-Natural: Blood levels and effects may be ↓ by St. John's wort.

Drug-Food: Blood levels and effects may be ↑ by grapefruit juice.