However , there was a quantitative interaction between progesterone level and effect of treatment : when progesterone level was > / = 10 ng/l , the efficacy of the combination of mifepristone and methotrexate was significantly higher than the combination of methotrexate and placebo , with an 83.3 % success rate ( 15/18 ) versus 38.5 % ( 5/13 ) respectively .
