Lorazepam solubility in and sorption from intravenous admixture solutions

Area of Science:

• Pharmaceutical Science
• Drug Delivery Systems
• Intravenous Admixtures

Background:

• Lorazepam is frequently administered intravenously, necessitating an understanding of its compatibility with intravenous solutions and administration components.
• Flexible polyvinyl chloride (PVC) bags and tubing are common in intravenous fluid administration, raising concerns about potential drug sorption.

Purpose of the Study:

• To determine the solubility of lorazepam in various aqueous intravenous solutions.
• To assess the extent of lorazepam sorption from intravenous admixtures into PVC bags and tubing.
• To evaluate the suitability of lorazepam for intravenous admixtures based on solubility and sorption characteristics.

Main Methods:

• Lorazepam solubility was measured in deionized water, 5% dextrose, lactated Ringer's, and 0.9% sodium chloride injections.
• Sorption of lorazepam into PVC bags was evaluated by measuring concentration changes over time at varying surface area-to-volume ratios.
• Continuous flow sorption through PVC tubing was tested at different administration rates.

Main Results:

• Lorazepam solubility varied across solutions, with values ranging from 0.027 to 0.062 mg/ml and demonstrating pH dependence.
• Lorazepam concentration in PVC bags decreased over time, following biexponential kinetics influenced by surface area-to-volume ratio.
• Significant lorazepam retention (>95%) was observed when administered through PVC tubing at various flow rates.

Conclusions:

• Lorazepam demonstrates adequate aqueous solubility for intravenous admixtures.
• Sorption of lorazepam by PVC components is slow, maintaining drug concentrations within acceptable limits for extended periods.
• Lorazepam is well-suited for dilution in intravenous admixtures for both intermittent and continuous infusion therapies.