Several improvements are disclosed for a drug delivery pack with dry reagent
in a housing, each of which can be employed independently or in conjunction with
others of the improvements. A novel spring is provided with two spring columns
extending in parallel between a spring top and a spring bottom. The spring is particularly
designed for fitting within the housing and compacting a dry reagent bed. A plunger
mechanism to ratchet housing portions between two positions. In one position, a
compression component adjacent the reagent bed is relatively uncompressed, such
that it does not "set" over time. When the user is about to use the drug delivery
device, the plunger is slid to compress the compression component so that it exerts
pressure on the reagent bed. A similar sliding mechanism can also divert a stream
of diluent through the housing from a priming path, where diluent bypasses the
reagent bed, to a functional path passing through and eroding the reagent bed.
Additionally, a method is provided for lyophilizing a liquid form of reagent within
the housing from which it is to be delivered, thereby avoiding separate lyophilization
and separate loading of dry form of the reagent.
