ABSTRACT
While the principal objective of the primary drying is to sublimate the solvent (generally water) from the matrix, the primary function of the secondary drying is to reduce the residual moisture content of the product to levels that will no longer support biological growth or chemical reactions. It is this stage of the lyophilization process that serves as a means for slowing the kinf?tic clock of the active constituent. This slowing of the kinetic clock accounts for the unusually long stability of a lyophilized product. A formulation such as a vaccine that can be stored effectively at 4-8°C for a few days can now be stored for months or years at ambient temperature.
