Exam 2: NSAIDs and Opioids Flashcards
Receptor most responsible for transmission of pain signals:
TRPV1
Function of B2 receptor:
Enhances TRPV1 activity
Function of prostanoid receptor:
Aids in depolarization of pain fiber via enhancement of voltage-gated Na+ channel
Function of opioid, cannabinoid, and norepi receptors:
Hyperpolarization of pain fibers via ↑ K+ retention
B2 receptors activated by:
Bradykinin
Laminae of Αδ fibers:
I, II, III, V
Laminae of C fibers:
I, II
Laminae of substantia gelatinosa:
II, III
Substantia gelatinosa is important because:
Richly populated with opioid peptides, receptors
Inhibitory interneurons
Area of the brain that descends neurons into substantia gelatinosa:
Nucleus raphe magnus
Opioid action in the brain:
Pre- and postsynaptically activate descending inhibitory pathways
Opioid action in the SC:
Directly on the dorsal horn
Opioid action in the periphery:
Peripheral terminals of nociceptive neurons
Opioid effect on pain perception:
Changes tolerance of pain without necessarily changing ability to perceive pain
Opioid effect on physiological response to pain:
Reduces neuroendocrine response:
SNS activation
Cortisol
Norepi release
Opioid use in anesthesia:
Attenuate SNS response to stimuli
Adjunct to IAs
Can be sole anesthetic (cardiac/trauma)
Periop/postop pain mgmt
Unique characteristics of opioids vs. other analgesics:
No max dose or ceiling effect
Tolerance develops with chronic use
Produces analgesia without loss of touch/proprioception/consciousness
Ex. of naturally occuring opioids:
Morphine, codeine
Ex. of semisynthetic analogs of morphine:
Heroin, dihydromorphone
Classifications of opioids:
Full agonist
Partial agonist
Mixed agonist/antagonist
Antagonist
MoA (presynaptic) of opioids:
Inhibits release of excitatory NTs (ACh, dopamine, norepi, substance P)
MoA (postsynaptic) of opioids:
Directly decreases neurotransmission
↑ K+ conductance: hyperpolarization
↓ Ca2+ channel activity: ↓ NT release
Modulation of phospholipase C
↓ cAMP
Opioid receptors:
Mu
Kappa
Delta
Mu-1 receptor locations:
Supraspinal*
Spinal
Peripheral
Effects of mu-1 receptor activation:
Euphoria Miosis Bradycardia (good in adults, not in peds) Urinary retention Hypothermia
Effects of mu-2 receptor activation:
Hypoventilation
Physical dependence
Constipation
Mu-2 receptor locations:
Spinal*
Some supraspinal
Kappa receptor locations:
Supraspinal*
Spinal*
Peripheral
Effects of kappa receptor activation:
Dysphoria
Sedation
Miosis
Diuresis
Drugs that work on kappa receptors:
Dynorphins
Opioid agonist-antagonists
Delta receptor locations:
Peripheral*
Supraspinal
Spinal
Effects of delta receptor activation:
Hypoventilation
Constipation
Urinary retention
Drugs that work on delta receptors:
Enkephalins
Two mutations to 6q24-q25 that can affect response to opioids:
Nucleotide 118 (10-20%) Nucleotide 17 (1-10%)
CYP450 mutation that alters metabolism of some opioids:
CYP2D6
Unpredictable PK and t1/2 of codeine, oxycodone, hydrocodone, and methadone
Drug least likely to be impacted by genetic variability:
Fentanyl
Ultra-rapid metabolizers at increased risk of:
PONV
and other side effects
CV effects of opioids:
Minimal impairment when used alone
Dose dependent bradycardia (vagal stimulation, direct SA/AV node depression)
Vasodilation/↓SVR (impairment of SNS tone, leading to ↓CO, ↓BP esp. with hypovolemia)
CV effects of morphine and meperidine:
Dose dependent histamine release
Bronchospasm
↓SVR, ↓BP
Exception to bradycardia effect of opioids:
Meperidine; causes tachycardia with direct myocardial depression
CNS effects of opioids:
Analgesia Euphoria Drowsiness Miosis Nausea No amnesia Decrease ICP and CBF - only if no hypoventilation though
Renal, GI, liver effects of opioids:
↑ tone of ureter and detrusor tone leads to urgency without ability to void
↓ catecholamine and cortisol release
Sphincter of Oddi spasm, ↑ biliary pressure
GI smooth muscle spasm
Constipation
N/V