Physiological Effects

In non-tolerant adults at analgesic doses, morphine decreases body temperature, decreases the release of stress hormones via its action on the pituitary gland, decreases respiration, suppresses the cough reflex, and can induce nausea. Opioids at therapeutic doses have little effects on blood pressure or heart rate but can cause orthostatic hypotension (commonly known as dizzy spells or head rushes), particularly in the elderly. Opioids decrease gastrointestinal secretions and gastrointestinal motility, reflecting their well-known anti-diarrheal properties. Opioids can also produce pruritis (itching) and suppress the immune system. At toxic doses, morphine and its derivatives can produce coma, constricted (pinpoint) pupils, and respiratory depression.

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