A drug delivery system for an implantable medical device and methods for making and using the same. Embodiments include a housing of an implantable component of the medical device and one or more at least quasi-solid drug-delivery modules that retain an at least quasi-solid state if not a solid state. The drug-delivery modules and component housing are physically distinct, and as such, may be manufactured independently of each other. The independently-manufacturable drug delivery modules each carry a drug, while the component housing has an exterior surface with one or more recesses formed therein. Associated module(s) and recess(es) are correspondingly dimensioned so that each module may be securely retained within an associated recess via, for example, an interference fit such as by physical interlocking or by friction fit. When so retained in a housing recess, the drug-delivery module and surrounding exterior surface of the housing form a contiguous component surface.
