A patient controlled analgesia (PCA) is a generic term which refers to a method allowing a. person in pain to deliver their own pain relief. The PCA is used for the more continuous. control of moderate to severe pain, where oral or intermittent analgesia would be less. effective. The intravenous route is referred to as PCIA in this document, as opposed to the. epidural route, referred to as patient controlled epidural analgesia (PCEA).