Narcotic (Opioid) analgesics Flashcards
What is the proper pharmacological term for narcotics?
Opioid analgesics.
How do opiates differ from opioids?
Opiates are directly derived from opium (e.g., morphine, codeine), while opioids include any drug or peptide that binds to opioid receptors and has opiate-like effects.
What is opium?
A substance extracted from opium poppy sap.
What are endogenous opioid peptides derived from?
Larger precursor proteins.
What are the main endogenous opioid peptides and their precursors?
Enkephalins (from proenkephalin)
Dynorphins (from prodynorphin)
Endorphins (from POMC - pro-opiomelanocortin)
Nociceptin/Orphanin FQ (from pronociceptin/OFQ)
What type of receptors are opioid receptors?
G protein-coupled receptors.
Where are opioid receptors located?
In the central nervous system (brain and spinal cord) and peripheral tissues.
What are common adverse effects of opioids?
Nausea, vomiting (due to stimulation of the chemoreceptor trigger zone)
Histamine release (causes itching, rashes, hypotension)
Constipation (due to decreased gastrointestinal motility)
Miosis (pinpoint pupils)
Bradycardia (except for meperidine, which causes tachycardia)
Respiratory depression (most dangerous effect, dose-dependent)
Dysphoria and psychotomimetic effects (kappa agonists)
Physical dependence, tolerance, and potential for addiction
What is the primary opioid receptor for morphine and most opioids, and what are its roles?
Mu (µ) receptor; mediates analgesia, euphoria, respiratory depression, and physical dependence.
Which opioid receptor is involved in analgesia and psychotomimetic effects?
Kappa (κ) receptor.
Which opioid receptor plays a role in analgesia and mood modulation?
Delta (δ) receptor.
Which opioid receptor regulates pain and mood but does not interact with classical opioid agonists?
Nociceptin/Orphanin FQ (NOP) receptor.
What are the primary therapeutic effects of opioids?
Analgesia (pain relief at spinal and supraspinal levels)
Sedation (calming effect, useful as an anesthesia adjunct)
Euphoria (reduces emotional response to pain, may contribute to addiction)
Antitussive (cough suppression)
Reduced gastrointestinal motility (treats diarrhea but can cause constipation)
Mild vasodilation (reduces cardiac workload in some conditions)
How does morphine reduce pain at the presynaptic level?
It inhibits calcium channels, reducing neurotransmitter release (glutamate, substance P, CGRP).
What intracellular signaling pathway does morphine inhibit?
It inhibits adenylate cyclase, reducing cyclic AMP (cAMP) and downstream pain signaling.
How does morphine affect postsynaptic neurons?
It activates potassium channels, leading to hyperpolarization and decreased neuron firing.
What makes heroin more potent than morphine?
It is more lipophilic, allowing it to rapidly cross the blood-brain barrier, making it highly addictive.
Why is morphine considered the standard opioid?
It is widely used for severe pain but undergoes significant first-pass metabolism.
Why is fentanyl significantly more potent than morphine?
It is 50-100 times more potent, has a rapid onset, and is used in anesthesia.
How does codeine provide pain relief?
It is a prodrug converted to morphine by CYP2D6 and is also used as an antitussive.
How does oxycodone compare to morphine in terms of bioavailability?
It has better oral bioavailability and is used for moderate to severe pain.
What makes methadone useful for opioid dependence?
It has a long half-life and NMDA antagonist activity, reducing withdrawal symptoms.
Why is hydromorphone preferred over morphine in some patients?
It is more potent and better tolerated in renal impairment.
Which opioids is a weak opioid agonist, inhibites serotinin and norepinerpherine reuptake
Tramadol
