Lyophilized injectable drugs are primarily therapeutic proteins, which must either be stored under special conditions or formulated to retain their efficacy from the time of manufacture until they are dispensed. Liquid protein drugs require refrigeration until dispensed – a requirement referred to as the ‘cold chain’. Alternatively, proteins can be formulated as powders (lyophilization). Lyophilized proteins must be reconstituted prior to injection. Lyophilized drugs are sold with reconstitution vial systems, or packaged in special injection devices (e.g., pens, needle-free injectors, two-part syringes) that allow reconstitution to take place in the device prior to injection.