Stability of vancomycin during prolonged infusion: seeking evidence to support nurses’ practices

Objective To evaluate the behavior of vancomycin solutions in different concentrations (5 mg/mL and 10 mg/mL) and under various temperature conditions (22ºC and 37ºC) at infusion times of zero (T0), two(T2) and four(T4) hours. Methods The experiment simulated clinical practice of vancomycin infusion. Antimicrobials were diluted at 5 and 10mg/mL, studied according to temperature variations (22°C and 37°C), and submitted to analyses immediately after preparation (T0), T2 and T4 hours of environmental exposure. The high-performance liquid chromatography method determined concentration and stability. A total of 108 concentrations and 36 pH measurements were analyzed for mean, standard deviation, ANOVA, and p≤0.05. Results The pH values did not show statistically significant variations during the four hours maintaining the acidic characteristic. There were no significant variations of vancomycin 5mg/mL at 22°C at T0 and T2, but there was a statistically significant concentration reduction at T4(<0.001). For vancomycin at 10mg/mL and 22°C, the active compound had an increase in concentration from T0 to T2, with a further decrease at T4(p=0.006); in 37°C there was a significant in concentration in T2 and T4(p<0.001). Conclusion Vancomycin at 5mg/mL showed significant concentration reduction in the fourth infusion hour. For vancomycin at 10mg/ml, there was an increase in concentration in the first two hours of analysis. There were statistically significant variations in vancomycin concentrations over time and in the experimental situations studied. Despite these variations, all changes remained within the 7% threshold accepted by the European Pharmacopeia, indicating that vancomycin stability is adequate for clinical use under the tested conditions.