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Questions and Answers
What is the primary mechanism by which morphine causes nausea and vomiting?
What is the primary mechanism by which morphine causes nausea and vomiting?
Which of the following is NOT a direct effect of morphine on the heart?
Which of the following is NOT a direct effect of morphine on the heart?
What is the effect of morphine on the release of GH and prolactin?
What is the effect of morphine on the release of GH and prolactin?
Which of the following is a Neuro-endocrine response to morphine?
Which of the following is a Neuro-endocrine response to morphine?
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What is the effect of morphine on the vasomotor centre?
What is the effect of morphine on the vasomotor centre?
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What is the primary cause of postural hypotension and fainting in morphine-treated patients?
What is the primary cause of postural hypotension and fainting in morphine-treated patients?
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What is the primary cause of death in morphine poisoning?
What is the primary cause of death in morphine poisoning?
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Which of the following is NOT a CNS effect of morphine?
Which of the following is NOT a CNS effect of morphine?
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What is the effect of morphine on the vasomotor centre?
What is the effect of morphine on the vasomotor centre?
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What is the effect of morphine on certain cortical areas and hippocampal cells?
What is the effect of morphine on certain cortical areas and hippocampal cells?
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What is the effect of morphine on the temperature regulating centre?
What is the effect of morphine on the temperature regulating centre?
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What is the effect of morphine on the cough centre?
What is the effect of morphine on the cough centre?
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What is the characteristic of sedation caused by morphine?
What is the characteristic of sedation caused by morphine?
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What is the effect of morphine on the respiratory centre in an otherwise healthy individual?
What is the effect of morphine on the respiratory centre in an otherwise healthy individual?
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What is the effect of morphine on mood and subjective effects?
What is the effect of morphine on mood and subjective effects?
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Why do patients in pain or anxiety perceive the effect of morphine as pleasurable?
Why do patients in pain or anxiety perceive the effect of morphine as pleasurable?
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What is a primary contributor to constipation induced by morphine?
What is a primary contributor to constipation induced by morphine?
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How does morphine affect the cardiovascular system?
How does morphine affect the cardiovascular system?
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Which of the following is a potential adverse effect of morphine on the respiratory system?
Which of the following is a potential adverse effect of morphine on the respiratory system?
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What is a common neuroendocrine response to morphine administration?
What is a common neuroendocrine response to morphine administration?
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What is the primary mechanism by which morphine causes opioid-induced nausea?
What is the primary mechanism by which morphine causes opioid-induced nausea?
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Which of the following statements regarding morphine's effect on the biliary tract is correct?
Which of the following statements regarding morphine's effect on the biliary tract is correct?
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Which of the following statements is TRUE about morphine's pharmacokinetics?
Which of the following statements is TRUE about morphine's pharmacokinetics?
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What is the primary reason for morphine's unreliable oral absorption?
What is the primary reason for morphine's unreliable oral absorption?
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Study Notes
Morphine Pharmacology
Central Nervous System Effects
- Nausea and Vomiting: Triggered by stimulation of the Chemoreceptor Trigger Zone (CTZ). Symptoms worsen with movement, especially in a full stomach.
- Miosis: Stimulation of Edinger-Westphal nucleus from central action, not from direct topical application of morphine to the eye.
- Cardiac Effects: Morphine stimulates the vagal center, leading to bradycardia.
- Cortical Stimulation: Higher doses can cause muscular rigidity, immobility, and potential convulsions due to inhibition of GABA release.
- Mood Effects: Promotes calming sensations; perceived as euphoric by patients in pain or addicts, while normal individuals may find it unpleasant.
- Respiratory Depression: Dose-dependent decrease in respiratory rate and tidal volume, particularly harmful in patients with preexisting conditions.
- Cough Centre: More sensitive to morphine than the respiratory center, leading to depression.
- Temperature Regulation: Depresses the temperature regulating centre causing potential hypothermia.
Neuro-Endocrine Actions
- Hormonal Influence: Reduces hypothalamic control over the pituitary; leads to decreased levels of ACTH, FSH, and LH, yet an increase in GH and prolactin.
- Sex Hormones: Clinical impacts are insignificant, except for heavy users who may experience reproductive issues.
- Anti-diuretic Hormone: Increases ADH release, reducing urine volume.
- Metabolic Effects: Can lead to mild hyperglycemia due to central sympathetic stimulation.
Cardiovascular Effects
- Vasodilation: Caused by histamine release, vasomotor center depression, and direct blood vessel action.
- Blood Redistribution: Shifts blood from the pulmonary to systemic circulation; therapeutic doses have minimal effect on blood pressure in normovolaemic patients.
- Postural Hypotension: May occur due to impaired vascular reflexes.
Gastrointestinal Effects
- Constipation: Resulting from various actions: decreased propulsive movements, increased segmentation, and sphincter spasms.
- Inability to Tolerate Defecation: Central action decreases attention to the defecation reflex, causing chronic constipation.
Actions on Smooth Muscles
- Biliary Tract: Spasm of the sphincter of Oddi may lead to increased intrabiliary pressure and biliary colic.
- Urinary Bladder: Increased tone in detrusor and sphincter causes difficulties in urination.
- Bronchoconstriction: Histamine release can cause bronchoconstriction, posing risks for asthmatics.
Pharmacokinetics
- Absorption: Oral bioavailability is low (1/6 to 1/4) due to first-pass metabolism; reliable parenteral administration is preferred.
- Plasma Protein Binding: Approximately 30% binds to plasma proteins, leading to a slow brain entry.
- Placental Transfer: Morphine crosses the placenta, potentially affecting the fetus more than the mother.
- Liver Metabolism: Primarily metabolized in the liver through glucuronide conjugation.
- Half-Life: Average plasma half-life is 2–3 hours, with the effect lasting 4–6 hours; almost complete elimination occurs within 24 hours.
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Description
This quiz explores the effects of morphine on the chemoreceptor trigger zone (CTZ) and the Edinger Westphal nucleus of the third nerve, including symptoms and reactions.
