Objective: To evaluate the success rate of single-dose intramuscular methotrexate [MTX] regimen for the treatment of ectopic pregnancy at Ramathibodi Hospital and identify predictive factors of treatment success.

Materials and Methods: The present study was a retrospective observational study of 141 patients diagnosed as ectopic pregnancy and treated by single-dose MTX regimen at Ramathibodi Hospital between October 2005 and September 2017.

Results: Of the 141 patients included in the present study, the authors found 103 patients were successfully treated with singledose MTX regimen (overall success rate 73.05%). The factors related to successful MTX treatment were pretreatment β-hCG level less than 3,000 mIU/ml (OR 3.07, 95% CI 1.20 to 7.84) and the decrease of β-hCG level on day 4 compared with day 0 (OR 7.45, 95% CI 2.84 to 19.58).

Conclusion: The single dose MTX regimen is a safe and effective treatment for ectopic pregnancy after a proper patient selection. The pretreatment β-hCG level and the change of β-hCG level between day 0 and day 4 are the important predictive factors that can predict the success of the treatment.

Keywords: Ectopic pregnancy, Methotrexate, Success rate