Patent ID: 7918843

Claim:
A controllable drug delivery device for delivering a liquid injectable drug, said device comprising: a drug reservoir; a drug administration device; a displacement-generating battery; a displacement sensor for producing a signal indicative of the actual displacement produced by said battery; a current-depletion circuit; a controller for applying a variable load across said battery; and a battery status unit coupled to the battery for determining at least one property of said battery that is indicative of battery displacement; wherein displacement generated by said battery under the control of said controller as current is depleted from the battery by the current depletion circuit displaces a wall of the drug reservoir thereby causing the reservoir to expel liquid injectable drug contained therein via said drug administration device, the inputs to said controller include both the displacement sensor and the battery status unit, such that two independent indications of the displacement achieved are available to said controller; the controller is responsive to a discrepancy between said two indications for determining that a malfunction has occurred, and the controller provides a substantially constant-current depletion of the battery and thereby causes said drug delivery device to deliver a substantially constant drug delivery rate.