1OUTPATIENT PARENTERAL ANTIBIOTIC THERAPY IN THE MANAGEMENT OF COMMUNITY-ACQUIRED LOWER RESPIRATORY INFECTIONS

An evolving theme of the practice of medicine in the late 1990s is to render the highest quality care at the lowest possible cost. Concepts that range far beyond the actual price of products is involved. These include decision making regarding need for hospitalization (usually the single largest cost associated with patient care) and the earliest possible safe discharge from the hospital. 35 Outpatient parenteral antibiotic therapy (OPAT) has provided an important mechanism to deliver intravenous antibiotic therapy outside of the hospital. By this means, an important historic reason for hospitalization may be negated for selected patients. By the use of this modality patients may either be treated completely out of the hospital or potentially have a hospitalization shorted if the sole reason to remain is to receive parenteral antimicrobials. Numerous studies have proven the cost-effectiveness of this modality, 2,28 and others have shown its safety when patients are appropriately selected. 24,25 Recommendations for the selection of patients for OPAT have been published. 8,53 Additionally, recent investigations confirm that the majority of patients with community-acquired pneumonia (CAP) and little risk of death prefer treatment outside of the hospital, but they are infrequently involved in the decision-making process. 12 A commentary regarding the use of OPAT for community-acquired lower respiratory infections was published within the past 5 years, which includes some data about patient selection for this disease. 51 Current philosophy is that the decision to employ OPAT is driven by adequacy of insurance, availability of appropriate resources within the community, and the clinical stability of the patient. Current dogma is that virtually any diagnosed disease can be treated outside of the hospital, provided the former criteria are met. Within the past several years the decision to employ OPAT has been further complicated by the availability of newer potent oral antibiotics that provide excellent bioavailability and have activity against most of the pathogens associated with respiratory infections. Such agents include newer quinolones (levofloxacin, sparfloxacin, grepafloxacin, trovafloxacin) with enhanced in vitro pneumococcal activity and activity against "atypical" organisms such as Mycoplasma pneumoniae and Chlamydia pneumoniae, 16,39,50 as well as azithromycin or clarithromycin. 6,9 There has also been a resurgence of interest in doxycycline as an agent for the management of community-acquired respiratory infections. 32 Additionally, recent studies have documented the efficacy of oral antibiotic therapy in the treatment of conditions historically thought to require parenteral antibiotics. Examples include chronic osteomyelitis and infective endocarditis. 23,27 Finally, other data now support the rapid transition from parenteral to oral therapy for many patients with CAP, thus negating the need for prolonged parenteral administration of anti-infectives (and presumably decreasing the need for OPAT). 46,47 In my opinion, although OPAT provides an important management strategy for selected patients with CAP and its complications, its need may be decreasing as advances in oral antibiotic therapy continue. Indeed, a recent statement denotes that "the Infectious Diseases Society of America and individual infectious diseases specialists must now lead the effort to educate both our colleagues and the public that oral treatment is appropriate for sick and even hospitalized patients and that it constitutes aggressive therapy whether in the hospital or at home." 34 The decision to utilize OPAT is complex and involves a number of decision points that relate to the patient, the disease and pathogen, the antibiotic, and the facilities available in the community. If conditions of medical stability, availability of appropriate community resources, and insurability are met, the absolute indications for OPAT as recommended by the author include (1) need for an agent available only by the parenteral route (eg, aminoglycosides, vancomycin); (2) lack of a functional gastrointestinal tract (eg, short bowel, nausea and vomiting) or inability to ensure drug absorption (eg, drug interactions or achlorhydria); and (3) infection at a site unlikely to be treatable with concentrations of a chosen antibiotic available after oral administration. As an example of the latter, serum concentrations of oxacillin given intravenously at a dose of 8–12 g/day are substantially higher than those achieved with the highest recommended doses of oral dicloxacillin. These issues, as they relate to community-acquired lower respiratory infections, are the focus of the following discussion. The disease focused upon is CAP, with some mention of the role of OPAT as it relates to cystic fibrosis. Within the context of these diseases, issues to be discussed include need for hospitalization (thus negating use of initial OPAT), early hospital discharge with consideration for OPAT, choice of antibiotic for specific infection types, and host considerations that may affect the decision to employ OPAT.