Such an alternative may be outside of extant regulatory requirements or medical best practices, in which case it may be viewed as salvage therapy.
Therapies considered to be drugs of last resort may at times be used earlier in the event that an agent would likely show the most immediate dose-response related efficacy in time-critical situations such as high mortality circumstances.
In cases presenting with suspected S. aureus, it is suggested by many public health institutions (including the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) in the United States) to treat first with empirical therapies for S. aureus, with an emphasis on evaluating the response to initial treatment and laboratory diagnostic techniques to isolate cases of drug resistance.
Due to the possibility of potential severe or fatal consequences of resistant strains, initial treatment often includes concomitant administration of multiple antimicrobial agents that are not known to show cross-resistance, so as to reduce the possibility of a resistant strain remaining inadequately treated by a single agent during the evaluation of drug response.
Vancomycin has long been considered a drug of last resort, due to its efficiency in treating multiple drug-resistant infectious agents and the requirement for intravenous administration.