For those just embarking on MTX I found this article sums up many questions I've seen on this forum quite nicely.
He also makes the following very clear:
Before starting, the information below does not constitute medical advice. Every person and every situation is unique. Please address questions about your care with your rheumatologist.
I hope it's of some help. I will also post another concerning Biologics ( forgive me for putting two posts up in one day--apologies)