Opioids mood change

Opioids share related pharmacologic attributes and exert a profound effect on the CNS and gastrointestinal tract. Mood changes, sedation, respiratory depression, nausea, vomiting, decreased gastrointestinal motility, dependence, and tolerance are evident in varying... 

Opioids produce analgesia without loss of consciousness, although drowsiness, changes in mood, and mental clouding occur. Responses to painful stimuh are blocked at several locations in the brain, resulting in both an alteration in the sensation of pain and a change in the affective response. The ability of a patient to perceive pain can remain the same while tolerance to pain is markedly increased (29). 

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