Outpatient Antibiotic Parenteral Therapy in Vulnerable Populations: People Who Inject Drugs and the Homeless

BACKGROUND

Serious infections that require prolonged parenteral antimicrobial therapy are common among people who inject drugs (PWID) and people who are homeless; and creating an outpatient antibiotic treatment plan can be challenging. We examined patient outcomes of our outpatient parenteral antimicrobial therapy (OPAT) program, with a focus on PWID and the homeless, to evaluate program function and add to the current scarcity of information on the clinical epidemiology and outcomes of bacterial infections in these high-risk populations.

METHODS

We conducted a retrospective cohort study of adult patients enrolled in the OPAT program at an urban public hospital. Patients were grouped by injection drug use status and housing status. Baseline demographics, infection types, and clinical outcomes were obtained from the medical record. Clinical cure was the primary outcome assessed in each patient group. Secondary outcomes included length of hospitalization, secondary bacteremia, line-tampering, and 30-day readmission.

RESULTS

A total of 596 adult patients with 960 diagnosed infections requiring OPAT services were enrolled in the study population. The most common infection diagnosed in PWID was bacteremia. Homeless PWID were more unlikely to achieve clinical cure compared to housed non-PWID patients, when unknown clinical outcomes were included in the analysis (47.2 vs 73.1%; RR 0.6, 95% CI 0.5-0.9, p=0.003). Excluding unknown clinical outcomes, homeless PWID achieve similar rates of clinical cure compared to non-PWID populations (89.3 vs 88.7%, RR 0.95, 95% CI 0.83-1.08; p=0.44). Homeless non-PWID patients achieved similar rates of cure compared to housed non-PWID patients (82.2 vs 73.1%; RR 1.1, 95% CI 0.9-1.3, p=0.12) and had good retention in care.

CONCLUSION

OPAT and medical respite are effective and successful treatment modalities for many patients, including the homeless. PWID are more likely to be lost to follow-up resulting in uncertain clinical cure rates but when appropriate follow-up is achieved, they have similar rates of clinical cure to non-PWID. Appropriate patient-selection criteria are necessary to optimize clinical outcomes.