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Morphine (Astramorph, Duramorph, MS Contin)

Opioid analgesic (high-alert; full mu-receptor agonist)

Mechanism of action

Activates mu-opioid receptors in the CNS to produce analgesia, sedation, and reduced sympathetic tone. Also causes histamine release (peripheral vasodilation, pruritus). Used for moderate-to-severe acute pain, cancer pain, palliative dyspnea, and as preload reduction in acute pulmonary edema.

Adverse effects

Life-threatening / NCLEX-tested

  • Respiratory depression — life-threatening, dose-dependent
  • Severe hypotension, especially with IV bolus or dehydration (histamine + sympathetic withdrawal)
  • Coma, sedation
  • Bradycardia
  • Severe constipation, ileus
  • Urinary retention
  • Tolerance, physical dependence, and opioid use disorder with prolonged use

Side effects

Common — what to teach

  • Drowsiness, sedation
  • Constipation (start a bowel regimen on day 1)
  • Nausea, vomiting (often improves after a few days)
  • Pruritus (histamine release; usually does NOT mean true allergy)
  • Miosis (pinpoint pupils)
  • Mild euphoria

Food & drug interactions

Other CNS depressants (benzodiazepines, alcohol, gabapentinoids, sedating antihistamines) compound respiratory depression and sedation — combination contributes to most opioid deaths. MAOIs cause severe hypotension or hypertension — avoid. Some serotonergic agents (TCAs, SSRIs) increase serotonin syndrome risk. Naloxone is the antidote.

Nursing implications

Assessment, monitoring, patient teaching

  • Assess pain (numeric scale + functional assessment), respiratory rate, oxygen saturation, and sedation level (POSS or RASS) before and 15–30 minutes after IV doses; before and ~1 hour after PO
  • Have naloxone (Narcan) immediately available for any inpatient on opioids; teach household members of high-risk outpatients to keep nasal naloxone at home
  • Hold for RR < 12 (or per institutional parameters) or excessive sedation; stimulate, support airway, give naloxone if needed
  • Start a scheduled bowel regimen (stimulant laxative ± stool softener) when starting any chronic opioid
  • Two-nurse verification for IV opioid wasting and high-risk doses; never leave drawn-up doses unattended
  • Counsel patients NOT to combine with benzodiazepines, alcohol, or other sedatives
  • Avoid in severe asthma, paralytic ileus, and head injury (raises ICP, masks neuro exam)

When to hold / contraindications

  • RR < 12 (or institutional threshold)
  • Excessive sedation (POSS 3–4)
  • SBP < 90 mmHg or symptomatic hypotension
  • Severe asthma exacerbation or active bronchospasm
  • Paralytic ileus or known severe constipation without a bowel plan
  • Acute head injury without trauma surgery direction

Memory anchor

"Morphine drops the respiratory rate first." Hold at RR < 12. Naloxone reverses. Histamine itch ≠ true allergy. Start the bowel regimen on day 1.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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