Background
Interstitial ectopic pregnancy is a rare but potentially life threatening condition. Of the three management options for this condition (expectant, medical and surgical treatment) methotrexate therapy in several regimens has been reported to be effective and beneficial.

Aim
To assess the safety and efficacy of intravenous bolus and infusion of methotrexate with folinic acid rescue for the treatment of interstitial ectopic pregnancy.

Materials and Methods
A retrospective cohort study of women with interstitial ectopic pregnancy treated with methotrexate at the Royal Brisbane and Women’s Hospital from April 2000 to December 2012. The treatment regimen comprised of a bolus dose of methotrexate 100 mg followed by 200 mg of methotrexate infusion over 12 h. Four doses of 15 mg oral folinic acid rescue were given post‐treatment. Success of methotrexate therapy was confirmed by either a negative serum beta‐human chorionic gonadotropin (β‐hCG) level or subsequent uneventful pregnancy.

Results
Of 33 women with interstitial ectopic pregnancy who were treated with this regimen, 31 (93.9%) were treated successfully, including women with a high β‐hCG level up to 106 634 IU/L and the presence of fetal cardiac activity. Minor side effects were documented in three cases.

Conclusions
Intravenous methotrexate therapy with folinic acid rescue is well tolerated and highly effective.