The drug is currently illegal in the United States, unless a doctor says it's ok...
If I were in constant pain... and that were the only option... controversy aside, the effects of pot... are they not similar to many other drugs prescribed?
I don't condone the use of pot for non medical reasons, as that is just drug abuse --- but medical... I don't think I could fairly cast shame on the act, when various other drugs have worse effects and those are also prescribed.