Implantable infusion pump and related methods

A method of treating a patient, the method comprising:

• determining a first dosage of an active substance that is configured to be delivered to a region of a brain;
• actuating an implantable medical device (IMD) disposed within a patient to deliver the first dosage to the region of the brain via a catheter having a proximal end coupled to the IMD and a distal end disposed within a skull of the patient;
• detecting an intracranial pressure of the region of the brain via a sensor of the IMD;
• determining whether the intracranial pressure is greater than a pressure threshold;
• and
• based on the intracranial pressure being greater than the pressure threshold, prevent the actuator from initiating delivery of a second dosage of the active substance.

A method of operating an implantable medical device (IMD) configured to be disposed within a patient and deliver an active substance to a catheter having a distal end positioned at a target area, the method comprising:

• determining a pressure within a treatment area;
• calculating an expulsion time to expel substantially all fluid within a chamber of an IMD;
• and
• setting an actuation time of a valve to be substantially equal to the expulsion time;
• wherein the actuation time of the valve includes a time that electrical current is actively delivered from a power source to the valve.