Stability of N-Acetylcysteine 60 mg/mL in Extemporaneously Compounded Injectable Solutions

Background: N-Acetylcysteine (NAC) administered by the IV route is the current treatment of choice for acetaminophen overdose. However, the protocol approved by health authorities in most countries has a complex dosing regimen, which leads to dosage errors in one-third of cases. Therefore, the Canadian Antidote Guide in Acute Care Toxicology and individual poison centres have begun to recommend a simplified regimen using continuous IV infusion. Unfortunately, no study has demonstrated the stability of IV solutions of NAC at concentrations above 30 mg/mL or in solutions other than 5% dextrose. Objective: To evaluate the stability of solutions of NAC 60 mg/mL in 0.9% sodium chloride, 0.45% sodium chloride, or 5% dextrose, stored for up to 72 hours in polyvinyl chloride (PVC) bags at 25°C. Methods: Solutions of the desired concentration were prepared from a commercial solution of NAC 200 mg/mL, with dilution in 0.9% sodium chloride, 0.45% sodium chloride, or 5% dextrose, and were then stored at room temperature in PVC bags for up to 72 hours. At predetermined time points (0, 16, 24, 40, 48 and 72 h), samples were collected and analyzed using a stability-indicating high-performance liquid chromatography method. A solution was considered stable if it maintained at least 90.0% of its initial concentration. Particulate matter count was also evaluated to confirm chemical stability. Finally, organoleptic properties, such as odour and colour, were evaluated to assess the stability of the solutions. Results: All solutions maintained at least 98.7% of their initial concentration. No obvious changes in odour or colour were observed. Moreover, particle counts remained acceptable throughout the study, according to the criteria specified in United States Pharmacopeia (USP) General Chapter 788>. Conclusions: NAC 60 mg/mL, diluted in 0.9% sodium chloride, 0.45% sodium chloride, or 5% dextrose and stored in PVC bags at 25°C, was chemically and physically stable for a period of at least 72 hours.