Update on the adverse effects of antimicrobial therapies in community practice.

It is difficult to identify and ascribe exact probabilities of most harms. However, all common antimicrobials create harms that must be considered when choosing whether to prescribe. Many adverse effects go unrecognized by prescribers. As side effects are inevitable, antimicrobials must be prescribed for as short a course as possible, only when the probability of benefit is greater than the risk of harm.