This is a major decision. Methotrexate is a major thing to consider.

But...it has been used this way, once a week dosing for about a decade now, with success.

To consider is good medical supervision. When blood work is done on time it
can reveal dangerous trends/changes before things get too toxic.

But the final decision is for quality of life benefit. If it does not perform well, it is best to move on. If the condition is not severe, disabling and agonizing the risk may not be worth the benefit either. So lots of things need to be considered.

You can read about it here:
http://www.rxlist.com/cgi/generic/mtx.htm

And here is the medwatch papers for one year of this drug...
Not a high number of damages considering other drugs that appear on this
site. But also to take into consideration is that this drug is not commonly used
either...so its numbers would be low.
http://patientsville.com/medication/...de_effects.htm