Is Mifepristone (Mistoliprone) suitable for a patient less than 6 weeks gestation who has recently taken Plan B (levonorgestrel)?

Mifepristone Prescribing for Early Pregnancy (<6 Weeks Gestation)

Mifepristone can be safely prescribed for medication abortion at less than 6 weeks gestation, and prior use of levonorgestrel (Plan B) does not contraindicate its use. 1, 2

Gestational Age Considerations

• Mifepristone combined with misoprostol achieves complete abortion rates of 95-97% before 9 weeks of gestation, making it highly effective at less than 6 weeks. 1
• The standard regimen consists of 200 mg oral mifepristone followed by 800 mcg misoprostol (administered buccally or vaginally), which is effective for medication abortion up to 77 days (approximately 11 weeks) gestation. 2
• Medical abortion can be performed safely in outpatient or home settings at this early gestational age. 1

Prior Levonorgestrel (Plan B) Use

• Any contraceptive method, including emergency contraception, can be started after completion of emergency contraceptive pills without concern for drug interactions. 3
• The CDC guidelines specify that after using emergency contraceptive pills, a barrier method should be used or abstinence maintained for 7 days when starting regular contraception, but this does not apply to mifepristone for abortion purposes. 3
• There is no evidence that prior levonorgestrel exposure affects mifepristone efficacy or safety for medication abortion. The mechanisms of action are distinct: levonorgestrel prevents ovulation/fertilization, while mifepristone blocks progesterone receptors to terminate an established pregnancy. 3, 2

Critical Safety Considerations

Absolute Requirements:

• Confirm gestational age via ultrasound (crown-rump length or mean sac diameter) or reliable menstrual history. 4
• Rule out ectopic pregnancy, particularly when risk factors exist or dating cannot be confirmed clinically. 2
• Assess Rh status: All Rh-negative women require anti-D immunoglobulin (50 mcg for abortion, or 300 mcg if smaller dose unavailable). 4

Key Contraindications:

• Previous cesarean delivery is a contraindication for misoprostol use due to uterine rupture risk (13% risk in third trimester, though data specific to first trimester is limited). 1, 4
• Confirmed or suspected ectopic pregnancy. 2
• Intrauterine device (IUD) in place (must be removed first). 2

Expected Clinical Course

• Cramping and bleeding are expected effects, with bleeding lasting an average of 9-16 days. 2
• Misoprostol adverse effects (low-grade fever, gastrointestinal symptoms) can be managed with NSAIDs or antiemetics. 2
• Rare complications include ongoing pregnancy (3-15% depending on gestational age), infection, hemorrhage, and need for unplanned uterine aspiration. 4, 2

Follow-Up Protocol

• Clinical follow-up at 7-14 days to confirm complete abortion using clinical history, serial quantitative beta-hCG levels, urine pregnancy testing, or ultrasonography. 4, 2
• Immediate contraceptive counseling is essential, as ovulation can resume 2-4 weeks post-abortion, and hormonal contraceptives can be started immediately. 4

Common Pitfalls to Avoid

• Do not delay treatment while waiting for additional testing if gestational age and intrauterine pregnancy are confirmed. 4
• Do not use expectant management in confirmed retained abortion—surgical evacuation is indicated. 4
• Do not assume teratogenicity: Current evidence does not support mifepristone as a teratogen if pregnancy continues after exposure, though misoprostol should not be given if the patient changes her mind. 5

State-Specific Considerations

While the question references "[STATE]," the medical evidence and FDA approval support mifepristone use at less than 6 weeks gestation regardless of location. However, clinicians must verify current state regulations, as legal restrictions on medication abortion vary by jurisdiction and may supersede medical guidelines. 1