From my own experience, I say that doctor is full of hot air. I have been on mtx for 17 years....yup, years. I started at 15 mgs, went to 25, then up to 50 and have been at 70 mgs for 11 1/2 years. SO....... I disagree with him that you can't get benefit from higher doses.
One thing I have learned from my oncologist is that this:
oral tablets - you get about 50% benefit of the mtx from this method as the liver detoxifies about 1/2 by going thru the gut.
injection - you get about 80 to 90% benefit from this before the liver detox's the blood.
IV - you get nearly 100% benefit this method as it is direct flow in the blood to the needed areas.
I had less side effects on injections than I did on tablets and felt better than with the pills
initially I had reaction with the iv, but it is now worked its way thru.
For me, prednisone is not an option medication and we had to find other ways to control the lupus. Mtx was my solution and has done quite well.
I'm sorry that your doctor is locked into an out of date concept of mtx and its use.
Sally