The invention provides a process for the preparation of a package comprising a sterilised bulk of a drug substance, such as penicillins (e.g. amoxicillin and ampicillin), a food product, a food ingredient, and a chemical, the process includes: providing the bulk of the drug substance; packing said bulk in a primary packing means and sealing said primary packing means, the void space in said primary packing means essentially consisting of an unreactive or inhibitory gas (e.g. carbon dioxide), thereby forming a package comprising said bulk of the drug substance; and exposing said package to electron beam treatment, thereby obtaining a package comprising a sterilized bulk of the drug substance. The invention also provides a package comprising a sterilized drug substance in a sealed primary packing means, said drug substance being selected from penicillins (e.g. amoxicillin and ampicillin), the void space of primary packing means essentially consisting of an unreactive or inhibitory gas.