A drug delivery device comprising a non-erodible, non-porous housing member defining a reservoir is provided. The reservoir is loaded with a dry formulation of a selected salt of a neuroleptic agent. The housing member has one or more porous partitions, where the pores of the partitions are sufficiently small to retain the insoluble powder particles within the reservoir yet large enough to allow diffusion of the active agent once the device is hydrated. A therapeutic dose of the drug is released from the device at a constant rate over a period of approximately 2-6 months.
