# Is It Possible to Optimize the Elaboration and Preservation of a Vancomycin Catheter Lock Solution?

## TL;DR

This study investigates whether a vancomycin catheter lock solution can be effectively frozen and stored for extended periods without losing its effectiveness.

## Contribution

The study introduces a novel approach to optimizing vancomycin catheter lock solution preparation by evaluating its stability and efficacy after freezing.

## Key findings

- Vancomycin concentration remained stable over 12 weeks of freezing but decreased after 2 weeks at refrigeration or room temperature.
- Minimum inhibitory biofilm concentration increased from 8 weeks for all tested strains.
- The solution can be stored for 12 weeks frozen followed by up to 1 week at refrigeration or room temperature.

## Abstract

Background/Objectives: Vancomycin (V) is widely used for catheter lock therapy. However, its ad hoc preparation in pharmacy departments involves discarding most of an intravenous vial and contributes to high workload. We aimed to assess the V concentration and minimum inhibitory biofilm concentration (MIBC) of a frozen V lock solution. Methods: Two V-2 mg/mL solutions were tested: (1) V + heparin 100 IU/mL and (2) V + citrate 2%. Solutions were frozen at −20 °C, followed by 48 h refrigeration, and analyses were performed at baseline and after 2, 4, 8, and 12 weeks (experiment 1). In addition, after the 12-week freezing period, solution 1 was also preserved for 1 and 2 weeks at both 4 °C and room temperature (experiment 2). V concentration was assessed by HPLC-DAD at 205 nm and validated with forced degradation tests. A <10% variation indicated significant change. MBIC was determined by XTT staining of 24 h biofilms exposed to decreasing concentrations of each solution. Microorganisms tested included methicillin-susceptible and -resistant Staphylococcus aureus (MSSA, MRSA), Staphylococcus epidermidis ATCC35984 (SE), and a highly biofilm-forming clinical S. epidermidis strain (SEclin). MIBC was defined as ≥50% reduction in metabolic activity. Results: In experiment 1, while V concentration remained stable over time, MIBC values varied, notably increasing from 8 weeks for all strains. Moreover, in experiment 2, significant reductions in both V concentration and MIBC were detected in the 2-week period. Conclusions: V lock solution appears to be able to be 12-weeks frozen followed by up to 1 week at refrigeration or room temperature. This facilitates the optimization of vial preparation in hospital pharmacy laboratories.