The present invention is directed to a fluid-imbibing dispensing device for the immediate or almost immediate and extended delivery of an active agent over a prolonged period of time together with the initially delayed pulse delivery of an active agent to a fluid environment of use. The dispenser comprises a housing having a first wall section and a second wall section in slidably telescoping arrangement with each other, which housing maintains its integrity in the environment of use; an internal compartment surrounded and defined by the housing; a first active agent delivery chamber within a portion of the compartment defined by the first wall section, the first delivery chamber including at least one active agent formulation, an exit means for providing communication between the active agent formulation and the environment, and a first expansion means for dispensing the first active agent formulation through the exit means to the environment immediately and over a prolonged period of time; a second active agent delivery chamber within a portion of the compartment defined by the first wall section and adjacent the open end of the first wall section, the second delivery chamber including at least one active agent formulation; and an expansion chamber within a portion of the compartment defined by the second wall section, for separating apart the first and second wall sections of the housing after exposure to the environment of use for dispensing the second active agent formulation to the environment in a pulse after an initially delayed period of time, the expansion chamber including a second expansion means and a partition layer or push plate.