Antimicrobial cycling: the future or a fad?

To assess the current evidence of the value of cycling of antimicrobials to control the emergence of resistance or to reverse existing resistance to antimicrobials.

Articles were obtained through a MEDLiNE search of the English-language literature from 1966 to January 2000. Additionally, references from retrieved publications were reviewed to identify further articles.

All investigations of switching between or cycling among antimicrobials were evaluated. Studies switching between or cycling among specific drugs or classes of drugs within institutional settings were included in this review.

Studies involving cycling among different aminoglycosides suggest that, although temporary decreases in resistance can be documented, resistance usually rebounds rapidly on completion of the cycle and return to the original agent. Switching between classes of antimicrobials has produced inconsistent results and has been shown to replace resistance to one agent with resistance to another. Mathematical models using both in vitro and clinical data have suggested that, due to residual resistance in the population, cycling among drug classes is unlikely to yield long-term reductions in antimicrobial resistance, especially if a high level of antimicrobial resistance exists.

Cycling among different antimicrobials to reverse resistance trends is currently not supported by published literature. Cycling to prevent the emergence of resistance may ultimately be more useful; however, no studies have evaluated this concept. Well-designed prospective studies are needed to evaluate the potential clinical value of antimicrobialcycling.