Antimicrobial therapy: principles of use

Antibiotics are unique among therapeutic agents. While their use is directed at treating or preventing microbial disease, their efficacy is continuously threatened by drug resistance. Such resistance is readily transmitted between micro-organisms that in turn may disseminate in the healthcare or wider environment. Infectious disease varies in severity by age and underlying risk factors. Choice of therapy requires a risk assessment to ensure safe and effective prescribing practice. A set of principles that supports good prescribing practice has evolved specific to infectious disease management. Drug selection is based on knowledge of its antimicrobial spectrum and the known or likely pathogens responsible for a target infection. The dose, route and duration of treatment are all affected by the nature of the drug and the infecting organism. The pharmacodynamic relationship between the susceptibility of the pathogen and the pharmacokinetic profile of the drug increasingly informs optimal dosage regimens. Inappropriate or unnecessary prescribing is associated with higher rates of resistance, adds to the cost of disease management and increases the risk of drug toxicity. Drug resistance requires a continuous updating of prescribing recommendations and often limits choice. Good prescribing practice is key to maintaining effective management of infectious disease for current and future generations.