41: Opiod Analgesics Flashcards
(42 cards)
what 5 things are opiods traditionally used for?
euphoria analgesia sedation relief from diarrhea cough suppression
opium combined with alcohol =
laudanum
the exudate from poppy seeds containing 20 biologically active components including morphine and codeine
opium
drug extracted from the exudate of the poppy
opiate
natural or synthetic drug that binds to opiod receptors producing agonist effects
opioid
term used to characterize pharmacological compounds used to treat moderate to severe pain
narcotic
natural opiods occur …
- in the exudate of the opium poppy
- as endogenous endorphins, enkephalins and dynorphins
all non-natural opiods are derived from…
morphine and precursor compounds
located outside the spinal cord and responsible for central interpretation of pain - supraspinal analgesia
Mu1
located throughout the CNS- brainstem and spinal cord
responsible for supraspinal and spinal analgesia, respiratory depression, constipation, physical dependence, and euphoria
Mu2
three endogenous opiod receptors
Mu
Kappa
Delta
what gprtn is assocaited with opiod receptor activation
Gi/Go
upon opiod receptor activation, the Gi/Go coupling results (3)
- inhibition of adenyly cyclase
- reduced opening of presynaptic voltage-gated Ca2+ channels resulting in loss of intracellular calcium and decreased release of neurotransmitters
- increase postsynaptic opening of K+ channels (hyperpolarization and decreased firing)
mechanisms of analgesia on the ascending pain pathways (3)
1) inhibition of afferent pain transmission (blockade of pain impulses from the periphery to the brain)
2) peripheral effects (activation of opiod receptors on distal ends of afferent neurons decreases their activation and excitability)
3) dorsal horn of the spinal cord (reduction in incoming pain signaling and reduction in pain signaling up the spinal cord)
how do opiods work presynaptically v. postsynaptically?
presynaptic : opiods block release of pain-mediating Nt from afferent neurons via inhibtion of Ca channels
postsynaptic: opioids inhibit activation of afferent neurons via increased K conductance that leads to hyperpolarization
how do opioids work in descending pathways?
opiods block inhibtior GABAergic interneurons to produce disinhibiton
leads to enhanced inhibition of nociceptive processing in the spinal cord and overall pain relief
site of action of opioids
periaqueductal gray-midbrain
rostral ventral medulla - brainstem
locus coeruleus - pons in brainstem
reduce both sensory and affective aspects of pain
analgesia
what special precaution needs to be taken with use of opiods in head trauma?
increased pCO2 –> reflexive cerebral vasodilation
respiratory depression is a general pharmacological effect of opioids and leads to reduction in respiratory center sensitivity to pCO2 tension
do opioids cause dilated or constricted pupils?
miosis - constriction of pupils
why do opiods cause cough suppression?
suppress the cough center in the brain – action is predominately via the brainstem chemoreceptor trigger zone
what is the main GI effect of opioids?
constipation
relieve diarrhea by decreasing gut motility and increasing the tone of intestinal smooth muscle
how do opioids affect the uterus and urinary tract?
diminished force of contractions in labor
urinary retention
what are the cardiovascular effects of opioids?
hypotension
bradycardia
