Outpatient parenteral antibiotic therapy: principles and practice.

Outpatient parenteral antimicrobial therapy (OPAT) refers to the administration of a parenteral antimicrobial in a non inpatient or ambulatory setting with the explicit aim of facilitating admission avoidance or early discharge. Whilst OPAT has predominantly been the domain of the infection specialist, the internal medicine specialist has a key role in service development and delivery as a component of broader ambulatory care initiatives such as "hospital at home". Main drivers for OPAT are patient welfare, reduction of risk of health care associated infection and cost-effective use of hospital resources. The safe practice of OPAT is dependent on a team approach with careful patient selection and antimicrobial management with programmed and adaptable clinical monitoring and assessment of outcome. Gram-positive infections, including cellulitis, bone and joint infection, bacteraemia and endocarditis are key infections potentially amenable to OPAT whilst resistant Gram-negative infections are of increasing importance. Ceftriaxone, teicoplanin, daptomycin and ertapenem lend themselves well to OPAT due to daily (or less frequent) bolus administration, although any antimicrobial may be administered if the patient is trained to administer and/or an appropriate infusion device is employed. Clinical experience from NHS Greater Glasgow and Clyde is presented to illustrate the key principles of OPAT as practised in the UK. Increasingly complex patients with multiple medical needs, the relative scarcity of inpatient resources and the broader challenge of ambulatory care and "hospital at home" will ensure the internal medicine specialist will have a key role in the future development of OPAT.