Stability of Lorazepam in 5% dextrose injection

Area of Science:

• Pharmaceutical Sciences
• Analytical Chemistry
• Drug Delivery Systems

Background:

• Intravenous admixtures are susceptible to drug adsorption onto storage containers.
• Polyvinyl chloride (PVC) bags are commonly used for parenteral drug storage.
• Accurate quantification of drug loss is crucial for therapeutic efficacy and patient safety.

Purpose of the Study:

• To investigate the adsorption of lorazepam in intravenous admixtures onto 50-mL PVC bags.
• To compare the accuracy of a spectrophotometric assay method with a newly developed high-performance liquid chromatography (HPLC) method for quantifying lorazepam loss.
• To identify factors contributing to discrepancies in measured drug loss.

Main Methods:

• Adsorption of lorazepam in intravenous admixtures onto 50-mL PVC bags was studied.
• Drug concentrations were measured using a literature-reported spectrophotometric assay.
• A novel HPLC assay method was developed and employed for comparative analysis.
• Adsorption kinetics and the effect of admixture volume were evaluated.

Main Results:

• The spectrophotometric method indicated a lorazepam loss of 7.7%–9.5%.
• The HPLC method revealed a significantly lower lorazepam loss of 4.9%–5.5%.
• Benzyl alcohol, a preservative in lorazepam injection, interfered with the spectrophotometric assay, causing overestimation of drug loss.
• Adsorption of lorazepam occurred within six hours, with no further significant loss thereafter.
• Varying admixture volumes (20–50 mL) did not significantly alter the extent of drug loss due to adsorption.

Conclusions:

• The spectrophotometric assay overestimates lorazepam loss due to interference from benzyl alcohol.
• HPLC is a more accurate method for quantifying lorazepam adsorption onto PVC bags.
• Understanding drug-container interactions is essential for ensuring accurate dosing of intravenous medications.