As care has shifted from the inpatient to outpatient setting, outpatient parenteral antibiotic therapy (OPAT) has become a mainstay of therapy. Advances in technology such as the elastomeric pump, also known as homeballs, ball pumps, or grenade pumps, have facilitated the use of OPAT since these devices don't require external tubing. They also generally have longer storage and stability specifications since they can be refrigerated or frozen.

A recent review examined the proper use of elastomeric pumps for the administration of OPAT. A PubMed search was conducted using the key words "elasomeric pump" and "antibiotic". Additional references were gathered from other sources (e.g., Congress abstracts). In total, 84 references were reviewed.

The authors identified the advantages, risks, and practices associated with the use of OPAT administered via elastomeric pumps.  

Among the advantages identified for the use of elastomeric pumps for OPAT were the availability for continuous and prolonged antibiotic infusions. This helps optimize the time above the minimum inhibitory concentration by improving the pharmacokinetic/pharmacodynamic (PK/PD) index. This also reduces the risk of resistance by decreasing the time within the mutant selection window (MSW), which is the time between the MIC and mutant prevention concentration (MPC). For time-dependent antibiotics, continuous infusion ensures high concentrations, which often exceed the MPC. For these reasons, elastomeric pumps are recommended as OPAT alternatives to carbepenems for enterobacteria resistant to third-generation cephalosporins.  An additional advantage to the continuous infusion is the ability to reduce the number of administrations for drugs with short half-lives.

Use of elastomeric pumps have been associated with improvements in the quality of life (QOL) of patients compared with the use of mechanical electronic devices. Their use is associated with improved mental status, although data on QOL in patients on OPAT is limited. Further work needs to be done to assess elastomeric pumps' role in preservation of mobility and physical activity. In some patients, while these pumps were associated with a better QOL, they were also associated with fatigue.

Clinical recovery rates have been found to be comparable with the use of elastomeric pumps for OPAT versus inpatient antibiotic treatment, although data are limited. They may be beneficial in patients with endocarditis or bone and joint infections who require prolonged treatment.

From a cost perspective, there are no publications comparing the expense associated with elastomeric OPAT to traditional antibiotic treatment in the home setting. While some have reported a reduction in cost by up to 50%, others have reported that for antibiotics with long half-lives (e.g., ceftriaxone or ertrapenem), the cost for a continuous or prolonged infusion system is not justified since these pumps are more expensive than gravity-driven infusion systems.

Despite potential advantages associated with elastomeric pumps, there are disadvantages as well. Factors in determining the stability and maximum infusion duration are based on the antibiotic, the aqueous form of the drug and its solubility, the concentration, the diluent and the pH, the temperature and infusion time. For example, carbapenems' degradation exceeds 10% at 25 degrees Celsius; however, piperacillin/tazobactam is stable for days at this temperature. There are solubility issues with amoxicillin powder at concentrations >150 mg/mL. Degradation can be concentration-dependent with ceftazidime and amoxicillin, with degradation occurring at a more rapid rate at increased concentrations. Also, diluents can affect stability as ceftazidime and penicillin G are more stable in normal saline or Ringer lactate than in dextrose 5%.

Another concern with the use of elastomeric pumps, besides the potential for reduced stability secondary to high concentrations, prolonged infusion durations, and potential for high temperature exposures, is that of degradation products. When broken down, ceftazidime produces pyridine, which can cause neurological and abdominal symptoms. Up to 11% of patients receiving OPAT via elastomeric pumps may experience adverse events, including cytopenias, renal insufficiency, or venous thrombosis. OPAT administered via elastomeric pumps may not be covered by insurance.

This article provides a list of antibiotics administered by elastomeric pumps and their stability duration based on temperature and maximum concentration following dilution. However, there is a paucity of information on the real-world use of elastomeric pumps, including data on drug instability for certain antibiotics, the potential for adverse events secondary to degradation products or overdosage, the effect of concentration and temperature variations, and an antibiotic's PK/PD that can justify its use from a cost perspective.

Pharmacists can play an active role in determining the best infusion options for their practice setting. Being familiar with parameters associated with the appropriate use of OPAT administered via elastomeric pumps can help provide patients with safe, effective, cost-justified, and convenient drug therapy.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

« Click here to return to Infusion Pharmacy Update.