Pharmacology-Opiates Flashcards
What are the different aspects of pain?
Dscriminative (hurts at a location), affective (emotion aspect)
How do C-fibers initiate the emotional aspects of pain?
They synapse on the paleospinothalamic tract. This tract goes to the intralaminar nuclei of the thalamus. The intralaminar nucleus sends axons to the reticular formation, sensory cortex, limbic system and singulate gyrus to modulate a dull, gnawing emotional pain.
A patient is in the ICU suffering from pain after amputation of one of his legs. Morphine-mediated inhibition of what regions would limit the anxiety and dread associated with the patient’s pain?
Locus ceruleus (anxiety & dread), raphe nucleus and dorsal horn of spinal cord, these all have Mu receptors. Binding of Mu receptors increases K+ permeability and decreases Ca2+ permeability. This hyperpolarizes the cell body and signal transmission is decreased.
You run into a bulldozer while reading a book and cut your head open. How does activation of the descending pain control pathway occur?
A-delta fiber stimulation -> Anterolateral spinothalamic tract -> Release of inhibitory enkephalin on the inhibitory GABA neuron -> activation of the periaqueductal gray -> inhibitory enkaphalin release on inhibitory GABA neuron -> activation of Raphe magnus -> activation of serotonin neuron -> serotonin release on enkephalin neuron in dorsal horn -> enkephalin release -> inhibition of A-delta and secondary fibers by increasing K+ permeability and decreasing Ca2+ permeability
What receptors does enkephalin bind to?
Mu receptors. These increase K+ permeability and decrease Ca2+ permeability.
How do TENS units and acupuncture work to control pain? How do we know this is how they work?
They send A-delta stimuli to the spinal cord that cause enkephalin release. We know this is how they work because these methods are ineffective when patients are given naloxone (opiate blocker)
What drugs are used to treat mild pain? Moderate pain? Severe pain?
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What is the major way our body gets rid of opiate drugs?
The liver puts glucuronide groups onto the opiate and they are excreted in the urine.
What is the foundation at which pharmaceutical companies begin when synthesizing opiods?
Tyrosine
Why is morphine more effective by injection?
75% will have glucuronide groups added during first pass metabolism and inactivate it.
What patients will be completely resistant to codeine?
Those with inactive CYP2D6. This enzyme is needed in the liver to remove the methyl group on codeine to turn it into active morphine.
Why do addicts prefer heroin to codiene?
It has two methyl groups that allow it to get into the brain easier where it is then converted to morphine.
What drug do you give to patients that have overdosed on heroin?
Naloxone (Narcan) it is an opiate receptor antagonist. Must be given by injection.
What is a highly active metabolite of morphine?
Morphine 6-glucuronide
What opiate agonists are synthetic opiates? How are these different from traditional opiates?
Fentanyl, sufentanil, meperidine and remifentanil. These are so potent that they can also be used as anesthetics.
Where do opiate drugs act when given systemically compared to locally?
Systemically: periaqueductal gray, raphe magnus, dorsal horn of spinal cord. Locally: Dorsal horn of spinal cord and sensory nerve endings. All of these locations have Mu receptors.
