Objectives To determine the physicochemical stability of pemetrexed diarginine in original vials, and after dilution in two commonly used infusion fluids (0.9% sodium chloride, 5% dextrose) in polyolefin bags, stored under refrigeration (2–8°C) or at ambient temperature (22–25°C) exposed to light.

Methods Stability of pemetrexed diarginine injection concentrate was determined in the original glass vials with closed-system transfer device. Diluted pemetrexed diarginine infusion solutions were aseptically prepared by dilution of pemetrexed diarginine concentrate with either 0.9% sodium chloride or dextrose 5% in polyolefin bags, in amounts yielding pemetrexed diarginine concentrations of 4, 9 and 12 mg/mL. Test solutions were stored under refrigeration (2–8°C) or at ambient temperature (22–25°C) exposed to light. Pemetrexed diarginine concentrations were determined throughout a 14-day storage period using a stability-indicating HPLC assay. In addition, test solutions were visually examined for colour change and precipitation.

Results Pemetrexed diarginine injection concentrate with closed-system transfer device is shown to be physicochemically stable for up to 4 days when stored under refrigeration and for 1 day at room temperature. A browning of the pemetrexed diarginine concentrate solutions appeared 0n day 2 when stored at ambient temperature and on day 5 under refrigeration. Pemetrexed diarginine diluted in dextrose 5% and 0.9% sodium chloride was physicochemically stable for up to 4 days when stored under refrigeration and for 1 day at room temperature. A browning of the diluted solutions appeared on day 2 when stored at room temperature and on day 5 when stored under refrigeration.

Conclusions Pemetrexed diarginine concentrate for solution stored under refrigeration with closed-system transfer device can be retained as a residual to reduce product losses. The analytical stability of pemetrexed diarginine in dextrose 5% and 0.9% sodium chloride under refrigeration enables our centralised unit to prepare this drug in advance.