[Completing a course of drug therapy is necessary to combat the infection, not to discourage emergence of resistance]

Abstract

For the treatment of infections, it is usually recommended to 'complete the course' so as to avoid the development of resistance. There is little evidence, however, for the exact duration of treatment. Only a few pathogenic microorganisms are able to develop resistance during exposure to effective antibiotic concentrations. Commensal flora are often destroyed during treatment, which can lead to colonisation with resistant mutants. Excretion of antibiotics in the urine will expose microorganisms in the environment, leading to resistance. Longer exposure will lead to more resistance. Only the time needed to clear up the infection should determine the duration of treatment and not the arbitrary length of an antibiotic dosage schedule.