<unk>  are<unk> s only used when all other options are exhausted.  Many of the best known are antibiotics, antivirals, or chemotherapy agents.  In those cases, they have the most potent antibiotic, antiviral, or anticancer effects, and/or are<unk> s for which no (or very few) resistant strains are known.  They are usually withheld from administration to prevent the development of resistance or due to unpleasant side effects.
Despite the fact that most of the notable<unk>  are antibiotics or antivirals, other<unk> s are sometimes considered<unk> , such as cisapride.
Drug of last resort
Generic drug
Mumps medical therapy
Blood substitutes
Macrolide
Home remedy
Protic solvent
Designer drug