A unit dose, gas-filled syringe is provided which is filled with gas and packaged in a gas barrier material prior to use to increase shelf-life, that is, to minimize gas leakage and dilution of the contents of the syringe. The syringe is filled with a selected gas and sealed inside a container made from a high gas barrier material. The container is also filled with the selected gas. The container material is selected to have a gas transmission rate sufficient to prevent the selected gas from diffusing out of the container into the atmosphere. The volume of gas in the container is greater that atmospheric pressure to prevent atmospheric contaminants from entering the container and syringe.