Methotrexate pharmacokinetics and effects in women receiving methotrexate 50 mg and 60 mg per square meter for early abortion

Mitchell D Creinin, M. A. Krohn

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


OBJECTIVE: Our goal was to evaluate the pharmacokinetics and safety of methotrexate in doses of 50 mg/m2 and 60 mg/m2 in regimens for early abortion. STUDY DESIGN: A randomized controlled trial was performed in women requesting an abortion at ≤49 days' gestation. Twenty women were treated with intramuscular methotrexate 50 mg/m2 (group 1) or 60 mg/m2 (group 2). Methotrexate levels were determined serially for the first 24 hours, then every 24 hours for 7 days. On the seventh day misoprostol 800 μg was administered vaginally. The misoprostol dose was repeated 24 hours later if abortion did not occur. RESULTS: Complete abortion occurred in 9 of 10 (90%, 95% confidence interval 56% to 100%) patients in group 1 and all 10 (100%, 95% confidence interval 69% to 100%; p = 0.99) in group 2. Methotrexate levels peaked within 1 to 2 hours and were nondetectable within 48 hours in all patients in group 1 and 72 hours in group 2. Both the maximum concentration of methotrexate and the area under the curve were significantly greater for group 2. Methotrexate clearance rates were 7.89 ± 1.98 L/hr and 5.55 ± 0.83 L/hr (p = 0.003), respectively. CONCLUSIONS: The serum levels of intramuscular methotrexate with 50 mg/m2 and 60 mg/m2 regimens indicate that these are safe treatment doses. Methotrexate 50 mg/m2 intramuscularly has the same clearance rates when administered during pregnancy as in a nonpregnant state, and maximum concentrations do not reach sustained toxic levels.

Original languageEnglish (US)
Pages (from-to)1444-1449
Number of pages6
JournalAmerican Journal of Obstetrics and Gynecology
Issue number6
StatePublished - 1997
Externally publishedYes


  • Abortion
  • Methotrexate
  • Misoprostol
  • Pharmacokinetics
  • Renal clearance

ASJC Scopus subject areas

  • Medicine(all)
  • Obstetrics and Gynecology


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