Objectives The aim of this study was to assess the stability of pemetrexed disodium (Alimta), reconstituted in 100 mL sodium chloride 0.9% w/v intravenous infusion bags (Baxter Viaflo) at two target bag concentrations (2.0 and 13.5 mg/mL) during storage at 2–8°C for 28 days (protected from light), followed by 24 hours at 25±2°C with 60±5% relative humidity (RH) (protected from light). This study was commissioned by NHS England and NHS Improvement to generate data to aid shelf life extensions for aseptic products compounded in National Health Service (NHS) hospital aseptic facilities.

Methods A high performance liquid chromatography (HPLC) assay was developed and validated to monitor pemetrexed concentration and related substance levels in accordance with NHS yellow cover document requirements. This assay and analysis of related substances was used alongside visual inspection, pH monitoring and sub-visible particle count analysis to monitor stability. The stability of three preparations of each concentration of pemetrexed disodium in Viaflo saline bags (0.9% w/v) was assessed at various time points.

Results Pemetrexed assay concentrations remained >97.0% of initial concentration at all points during the study (including the period at elevated temperature). Appearance remained consistent with the Summary of Product Characteristics, particle count data remained within the British Pharmacopoeia limits, and pH remained within 0.43 units of T=0 at all times. The increases in related substance levels during the study were found to be the limiting factor for shelf life assignment.

Conclusion The data for appearance, pH, sub-visible particle count analysis and pemetrexed assay would support a shelf life of 28 days stored at 2–8°C (protected from light) followed by 24 hours at 25±2°C with 60±5% RH (protected from light). However, given the increase in related substance levels, a shelf life of 21 days stored at 2–8°C (protected from light) was deemed to be appropriate.