A drug delivery device includes a first portion, formed primarily from elastomeric material, and a closure portion, cooperating with an opening of the first portion so as to complete an inflatable drug reservoir. The closure portion extends into the first portion inwards from the opening, defining at least one region of overlap between the first portion and the closure portion. The first portion and the closure portion define an outlet flow path for releasing a drug from the drug reservoir, with at least part of the outlet flow path passing between the first portion and the closure portion in the region of overlap. The region of overlap is disposed so as to be acted upon by a pressure within the drug reservoir thereby changing a flow impedance of the outlet flow path to provide an at least partially pressure compensated flow regulating mechanism.
