Methotrexate: The Pharmacology Behind Medical Treatment for Ectopic PregnancySTIKA, CATHERINE S. MDClinical Obstetrics & Gynecology: June 2012 - Volume 55 - Issue 2 - p 433–439 doi: 10.1097/GRF.0b013e3182510a35 Ectopic Pregnancy Abstract Author Information Previously established as a chemotherapeutic agent for decades, methotrexate has been adapted for use as a medical therapy for unruptured ectopic pregnancies. Its mechanism of action, competitive inhibition of folate-dependent steps in nucleic acid synthesis, effectively kills the rapidly dividing ectopic trophoblast. However, the same action on normal cells is the basis for many of its adverse effects. Department of Obstetrics & Gynecology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois The author declares that there is nothing to disclose. Correspondence: Catherine S. Stika, MD, Northwestern Medical Faculty Foundation, 680 North Lake Shore Drive, #1015, Chicago, IL. E-mail: email@example.com © 2012 Lippincott Williams & Wilkins, Inc.