A battery-powered nonprogrammable device designed to be implanted in a patient for the storing and subarachnoid administration of narcotics/drugs (e.g., morphine sulfate, baclofen) to manage intractable pain and muscle spasms of malignant or non-malignant origin. This implantable infusion pump (IIP) may enable delivery of a bolus of medication, typically patient-controlled with mechanical restrictions that limit the refill rate of the device, or it may provide a constant flow of medication at a factory-set rate. The device typically consists of a refillable drug reservoir, usually implanted under the skin of the lower abdomen, and a connected catheter placed into the spinal fluid space.