Techniques used to freeze-dry "small doses" of thrombin

In can be difficult to maintain the moisture level of small quantities of freeze-dried product contained in vials. We have observed that over a period of time a gradual increase in the residual moisture level in Thrombin vials containing small quantities of the freeze-dried product can sometimes be seen. No change in Thrombin potency has been observed. Investigations into the cause and resolution of this situation resulted in (1) modification of the freeze-drying cycle for vials containing small quantities of Thrombin and (2) incorporation of a special drying cycle for vial stoppers.