The use of ampicillin in the outpatient setting has traditionally been avoided because of the short half-life and instability in solution of this drug. However, recent in vitro data and two case series support the safe and effective administration of ampicillin by continuous infusion in the community. Therapeutic drug monitoring (TDM) of beta-lactam antibiotics can be used to optimise antibiotic exposure and ensure adequate clinical responses. A case series is presented of patients receiving ampicillin via prolonged infusion in the outpatient setting, with TDM to ensure adequate plasma antibiotic levels were achieved. Three patients who received ampicillin by continuous infusion under the Outpatient Parenteral Antimicrobial Therapy (OPAT) program are described, including details of antibiotic dose and steady-state plasma drug concentration as measured by high-performance liquid chromatography. All three patients had an infection with ampicillin-susceptible Enterococcus faecalis; one patient had post-partum endometritis, one had urosepsis and one had a complex polymicrobial bone and joint infection. Adequate plasma drug levels were achieved in all patients. Management of the antibiotic temperature and infusion times, and appropriate timing of drug levels in the community were required. Two patients achieved clinical cure, while the third required further surgical debridement and antibiotic therapy. TDM in this setting enabled the contemporaneous management and dose alteration of ampicillin. Ampicillin may be a safe and effective drug when administered by continuous infusion with appropriate TDM in the community setting.
Keywords: Ampicillin; OPAT; therapeutic drug monitoring.
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