The drug causes early abortion by blocking the vitamin folic acid in fetal cells so they cannot divide. Used in combination with misoprostol, it is about 95 percent successful in terminating early pregnancies. Methotrexate regimens have been developed to terminate intrauterine pregnancies only quite recently, and involve off-label use of the drug. For this reason, no single standardized protocol has been set forth. Several methotrexate-misoprostol protocols are currently used.
All protocols involve a minimum of two clinic visits.
All require women to be of good health with no contraindications to surgical abortion and no history of chronic kidney or liver disease, anemia, acute inflammatory bowel disease, or uncontrolled seizures. Regardless of which protocol is used, on the first visit the woman receives 50 mg methotrexate per square meter of body surface, injected into the muscle of her hip. This is followed by 800 mg misoprostol inserted vaginally. One option is to take four 200 mg tablets and hold the tablets in place with a tampon. The tampon should be left in place for 12 hours or until active vaginal bleeding begins.