Outpatient parenteral antibiotic therapy: not so crazy after all these years.

Outpatient parenteral antibiotic therapy, or OPAT, has emerged as an essential component of our health care delivery system in the United States. The idea evolved from the initial use of an indwelling Silastic catheter for the successful delivery of home total parenteral nutrition for a patient with massive mesenteric thrombosis with no complication of infection after more than 23 months of use. Subsequently, pilot studies in Canada and in the US suggested an alternative to inpatient IV antibiotic delivery via the use of OPAT, using standard IV antibiotics. In the early 1980s, Dr. Donald Poretz and colleagues at Fairfax Hospital in Falls Church, VA, recognized the potential value of outpatient antimicrobial therapy for clinically stable patients with diseases such as bacterial endocarditis and osteomyelitis and were successful in convincing third party carriers in the greater Washington, DC area to provide payment for OPAT. Their initial open study documented both the efficacy and especially the safety of this novel approach. While OPAT began to gain acceptance among physicians and insurance carriers alike during the mid-1980s, several developments facilitated wider utilization. First, the pharmaceutical industry’s development of antimicrobial agents with longer half-lives, such as ceftriaxone, made once-a-day dosing of outpatient therapy possible. Secondly, technological improvements in IV devices, such as the midline and percutaneous IV cutaneous catheters (PICC), broadened the access of health care providers who could install and/or maintain IV delivery over a longer period of time. As a result, patients with emerging diseases, those with infectious complications of HIV-1 disease and chronic osteomyelitis for example, could have continuous IV access for months instead of weeks. Of the serious infectious diseases treated via OPAT, only those with bacterial meningitis have had results that suggest careful selection of patients. Recent reports estimate that over 250,000 patients each year are served by OPAT in the US. Traditionally, serious infections with Staphylococcus aureus required 2 to 6 weeks of IV, anti-Staphylococcal antimicrobial therapy in health care facilities. The article by Wynn et al, in this issue (see p. 590) details the results of over 1,500 patients with methicillin-sensitive S aureus (MSSA) infections treated with OPAT. The data reinforce the efficacy of OPAT even with the most serious of infectious presentations of MSSA, such as osteomyelitis, endocarditis, wound infections, and bacteremias. In addition, the adverse event rates (due to either the antimicrobial agents prescribed or complications of the IV catheters) are comparable to those in health care facilities, reinforcing the relative safety of OPAT. Unexpected results included the efficacy of ceftriaxone, generally not regarded as a first line anti-MSSA antimicrobial agent, while the data reinforce prior observations that, Vancomycin is not the optimal antimicrobial agent for MSSA. Utilizing a multicenter database such as the OPAT registry may be very useful in providing clinical outcome data of a large enough scale to reveal therapeutic differences that would not be observed in single-center or small multicenter clinical trials. Cautious interpretation of retrospective observational data should always be emphasized due to the potential for bias in outcome reporting and incomplete data collection. What is next for OPAT in our health care delivery system? The increasing frequency of community-acquired methicillin-resistant S aureus (CA-MRSA) presents a challenge to caregivers and facilities alike. The data by Wynn et al, document the successful delivery of antimicrobials that treat MRSA as well as MSSA, providing hope that CA-MRSA may be treated successfully by OPAT as well. Secondly, with the aging of the US population, cost savings to the Medicare system, as concluded by prior studies, could be achieved by broadening the currently approved indications for OPAT among those insured by our government health care system.