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Questions and Answers
What is the primary mechanism of action of Tramadol?
What is the affinity of Tramadol for µ opioid receptor?
Why should Tramadol not be given to patients taking SSRI therapy?
What is the equianalgesic dose of i.v. tramadol to i.m. morphine?
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Which drug is indicated for reversing neonatal asphyxia due to opioid use during labor?
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Which opioid is a pure antagonist that blocks all types of opioid receptors?
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Which part of the Central Nervous System (CNS) does morphine act on to cause nausea and vomiting?
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What is a neuro-endocrine action of morphine?
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What is a pharmacological action of morphine on the gastrointestinal tract (GIT)?
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Where is morphine metabolized in the body?
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What are adverse effects of morphine?
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What are idiosyncratic reactions associated with morphine?
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What are some precautions and contraindications for using morphine?
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What is a characteristic of heroin compared to morphine?
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In what context is transdermal fentanyl primarily used?
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What is a characteristic of pethidine compared to morphine?
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Study Notes
- Morphine acts on various parts of the Central Nervous System (CNS), including the Chemosensitive Trigeminal Zone (CTZ) causing nausea and vomiting, Edinger Westphal nucleus leading to miosis, vagal center causing bradycardia, and cortical and hippocampal areas which exhibit excitation.
- Morphine has neuro-endocrine actions, including decreasing levels of Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Adrenocorticotropic Hormone (ACTH), while increasing levels of Prolactin and Growth Hormone (GH), and lowering sex hormones and corticosteroids on a short-term basis.
- Morphine induces CVS vasodilatation due to decreasing blood vessel tone, histamine release, and depression of the vasomotor center.
- Morphine has pharmacological actions on the GIT which involve constipation as a prominent feature, spasm of the sphincter of Oddi, leading to increased pressure and possible biliary colic, urinary urgency and difficulty in micturition, uterus slightly prolongs labour, and bronchoconstriction due to histamine release.
- Morphine has low oral bioavailability, is widely distributed in the body, freely crosses the placenta, is metabolized in the liver by glucuronide conjugation, and undergoes enterohepatic circulation.
- Adverse effects of morphine include sedation, mental clouding, lethargy and dysphoria, occasional vomiting, common constipation, respiratory depression, blurring of vision, urinary retention, hypotension (in hypovolemic patients), and apnea in newborns.
- Morphine has idiosyncratic reactions like urticaria, itching, and swelling of the lips.
- Morphine has various precautions and contraindications, including infants and the elderly, respiratory insufficiency, bronchial asthma, head injury, hypotensive states and hypovolemia, undiagnosed acute abdominal pain, and unstable personalities prone to addiction.
- Morphine interacts with other drugs, including opioids, phenothiazines, tricyclic antidepressants, monoamine oxidase inhibitors, amphetamine, and neostigmine, morphine delays gastric emptying, and retards absorption.
- Morphine and its congeners have various uses, including as an analgesic, transdermal fentanyl, preanaesthetic medication, relief of anxiety, myocardial infarction, internal bleeding, and for acute left ventricular failure.
- Tolerance and dependence on morphine are high, with both mainly pharmacodynamic and pharmacokinetic components.
- Morphine withdrawal manifests as marked drug seeking behavior, physical manifestations of lacrimation, sweating, dehydration, anxiety, fear, restlessness, mydriasis, tremor, rise in BP, palpitation, and can be precipitated by opioid antagonists like naloxone or nalorphine.
- Codeine, a chemical similar to morphine, is less potent as an analgesic, is a partial agonist at μ opioid receptors, is less efficacious than morphine, but is more selective as a cough suppressant.
- Heroin, a highly addictive drug related to morphine, is about three times more potent, enters the brain more rapidly, but has a similar duration of action. It is less sedative and less hypotensive than morphine.
- Pethidine, a chemically unrelated drug to morphine, interacts with μ opioid receptors and shares similar actions to morphine, but is less potent, less effective as a cough suppressant, and has fewer spasmodic actions.
- Fentanyl, a pethidine congener, is 80–100 times more potent than morphine, produces few cardiovascular effects, and enters the brain rapidly. It is used primarily in anaesthesia and has a short duration of action.
- Transdermal fentanyl is used for chronic pain management in cancer or terminal illness patients.
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Description
Learn about opium, poppy, and their active principle morphine. Understand the classification and pharmacological actions, pharmacokinetics, adverse effects, precautions, and clinical uses of opioid drugs.
