Resistant to medication
Merriam-Webster Online Dictionary
refractory (adjective)1.
resisting control or authority - stubborn unmanageable
2.
a) resistant to treatment or cure - a refractory lesion
b) unresponsive to stimulus
c) - immune insusceptible after recovery they were refractory to infection
3.
difficult to fuse, corrode, or draw out , especially capable of enduring high temperature unruly
a refractory person or thing , especially a heat-resisting ceramic material