What are the criteria for using methotrexate (MTX) for inducing abortion?

Criteria for Using Methotrexate for Inducing Abortion

Methotrexate should only be used for medical abortion in pregnancies ≤63 days (≤8 weeks) gestation, with optimal results in pregnancies ≤49 days (≤7 weeks) gestation, and requires strict adherence to follow-up protocols to ensure complete abortion. 1, 2, 3

Patient Selection Criteria

Required Criteria

• Confirmed early pregnancy ≤63 days from last menstrual period 2, 3
• Hemodynamically stable patient 1
• No evidence of ectopic pregnancy 1
• No contraindications to methotrexate therapy 4
• Patient willing and able to return for multiple follow-up visits 5
• Patient able to access emergency care if complications arise 1

Contraindications

• Pregnancy >63 days gestation 2, 3
• Confirmed or suspected ectopic pregnancy 1
• Known hypersensitivity to methotrexate 4
• Active liver disease or significant hepatic impairment 4
• Blood dyscrasias (bone marrow hypoplasia, leukopenia, thrombocytopenia, significant anemia) 4
• Immunodeficiency syndromes 4
• Alcoholism or chronic liver disease 4
• Breastfeeding mothers 4
• Inability to comply with follow-up requirements 5

Treatment Protocol

Dosing Regimen

• Standard dose: 50 mg/m² of methotrexate intramuscularly 5, 2
• Alternative oral dosing: 25-50 mg orally (25 mg has shown similar efficacy to 50 mg) 6
• Most effective when combined with misoprostol:
  • Methotrexate followed by misoprostol 800 μg vaginally 3-7 days later 2, 6, 3, 7
  • Success rates of 90-96% when combined with misoprostol 2, 3
  • Methotrexate alone has higher failure rates (17.2% vs 10.9% with combination) 8

Medication Precautions

• Avoid folic acid supplements during treatment (counteracts methotrexate's action) 5
• Avoid concurrent use of NSAIDs and aspirin (potential for lethal interactions) 5, 4
• Avoid oral antibiotics during treatment (may interfere with methotrexate absorption) 4

Follow-up Protocol

Monitoring Requirements

• β-hCG measurements on days 1,7, and 14 after methotrexate administration 3
• Continue monitoring with high-sensitivity urine hCG tests every 2 weeks until negative (<10 IU/L) 3
• Clinical evaluation for signs of complete abortion or complications 1
• Expected timeline: complete abortion may take up to 23 days with methotrexate alone, or approximately 12 days with methotrexate-misoprostol combination 8

Success Criteria

• Complete abortion defined as vaginal bleeding and β-hCG value <10 IU/L without surgical intervention 3
• Expected success rates: 90-96% with methotrexate-misoprostol combination 2, 3

Important Considerations

Potential Side Effects

• Gastrointestinal: nausea (70%), vomiting (23%), diarrhea (46%) 3
• Vaginal bleeding: average duration 11.2 days (7.1 days of bleeding + 4.1 days of spotting) 7
• Abdominal pain (common with misoprostol) 3
• Rare but serious: stomatitis, bone marrow suppression 1

Patient Counseling

• Women must avoid pregnancy for at least 3 months after methotrexate treatment due to teratogenic risk 5, 4
• Patients should be informed about the expected timeline for abortion completion 8
• Patients should understand the need for multiple follow-up visits 5
• Emergency warning signs requiring immediate medical attention: severe abdominal pain, heavy vaginal bleeding, fever, dizziness 1

Failure Management

• Surgical intervention is indicated if:
  • Complete abortion does not occur
  • Excessive bleeding develops
  • Signs of infection emerge
  • Pregnancy continues despite treatment 1, 3

Special Considerations

• For Rh-negative women, anti-D immunoglobulin should be administered to prevent alloimmunization 1
• Gastrointestinal symptoms may mimic complications; rule out abortion failure before attributing symptoms solely to medication side effects 5

The most effective protocol combines methotrexate with misoprostol, as methotrexate alone has higher failure rates and longer time to complete abortion 8, 2.