A battery-powered infusion device designed to deliver intermittent bolus doses of opioid medications [e.g., Fentanyl, Demerol (meperidine), Morphine, or Hydromorphone] upon patient demand (i.e., when activated by the patient when he/she requires pain relief), or in a slow, continuous mode for regional anaesthesia. A patient-controlled analgesia (PCA) infusion pump is used to infuse drugs into an operative site, or subcutaneously for postoperative pain management. It is used for hospital/home-use and can be worn by the patient for ambulation. It will incorporate safety mechanisms to prevent the patient overdosing; some types will employ computerized ambulatory drug delivery (CADD) software.