Abstract: A device for monitoring and controlling the operation of a motorized syringe to dispense a predetermined drug dosage comprises, according to one aspect of this invention, a combination of a trigger, a first signal monitor, a first timer, a second signal monitor and a second timer. The trigger is operable by the patient to initiate a demand signal indicative of a demand for an individual drug dose. The first signal monitor serves to record the total number of occasions on which a demand signal is initiated by operation of the trigger. The first timer receives the demand signal and selectively rejects the demand signal or emits the demand signal as an inject signal. The second signal monitor records the total number of occasions on which the first timer emits a demand signal. The second timer receives the inject signal and is operable upon receipt of the inject signal to activate a motorized syringe for a preselected time period to dispense a predetermined individual dose of drug.