A drug or fluid delivery device includes a pump having a control module. A cassette is removably mounted to the control module. A reservoir is contained within the cassette, and contains a fluid to be delivered to a patient. A protrusion extends from an interior surface of the cassette, creating and maintaining a crease in the reservoir as the fluid is emptied therefrom, thereby creating a fluid path along which the fluid travels to reduce occurrences of the reservoir deleteriously sealing off pockets of fluid as the reservoir is emptied.
