<prompt> Methotrexate is best suited when b-hCG concentration is:5000 IU6000 IU7000 IU10,000 IU  <response>: Ans. is a, i.e. 5000 IU.Ref. Williams Obs 25e pg 378Failure rate of methotrexate is 3.8. If b-hCG levels are 5000 IU but rise to 14 if levels are between 5000-10,000. 