The term "necessary drugs" refers to medications that are essential for treating certain health conditions and maintaining good health. Full definition
It specifically covers «medically necessary drugs and medicines» which were «obtained only by prescription». (blg.com)
A diagnosis of breast cancer brings a complex range of emotional and practical concerns, and being unable to access necessary drugs can only cause extra anxiety at an already difficult time. (politics.co.uk)
We should know, for example, how many weeks» worth of necessary drugs hospitals have «in stock.» (canadianbusiness.com)