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opioid analgesics

Terms

undefined, object
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primary drug target of opioids
mu receptor
endogenous peptides with opioid activity are made from cleavage of what proteins
Proopiomelanocortin POMC
proenkephalin
prodynorphin
biologically active metabloits of pre opioid-like proteins
metenkephalin
leu-enkephalin
dynorphin A and B
mu receptors effector systems
K channels (opened by agonist)
Ca channels (agonist reduce opening)
adenylate cyclase (inhiibtion)
K channel activation plus Ca channel inhibition plus adenylate cAMP reduction cause
reduced amount of transmitter release and therefore causes presynaptic inhibition
K channel activation causes
inhibition of the discharge rate of neurons
POSTSYNAPTIC INHIBITIONNNNNN
allodynia
pain caused by previously inocuous stimuli, often associated with inflammation, like in gout
algogen
activators of peripheral nociceptors
bradykinin, histamine,
serotonin
mechanism of opioid analgesia
spinal mechanism:
dorsal horn contains opioid interneurons that gate nociceptive inputs by pre and postsynaptic inhibiton
descending inhibition:
pathways from the pons potentiate spinal analgesia by opiates (serotonin and noradrenalin)
which is relieved better by morphine, continuous dull pain or sharp intermittent
continuous dull
true/false: morphine decreases pain, touch, vibration and temperature sensations to equal degree
false, pain is decreased much more than other sensory modalities
morphine causes respiratory depression, particularly affecting the ______ or respiration
rate
mechanism of action of morphine that causes respiratory depression
acts on brain stem respiratory centers and reduces responsiveness to pCO2
main drive for respiration in a morphinized patient
hypoxic stimulation of carotid chemoreceptors
morphines effect on cough reflex and GI
antitussive
produces nausea and vomiting
effects of morphine on neuronendocrine system
hypothermia
decreased urinary output
hyperglycemia
decreased release of pituitary gonadotrophic hormones
morphine effect on pupils
miosis (Edinger westphal nucleus)
at extremely high doses, morphine may cause
convulsions and seizures
morphine effects on CV system
peripheral vasodilation (decrease of sympathetic tone)
postural hypotension
morphine affect on GI
acts on nerve plexi of GI
decreases propulsive peristaltic contractions
increases tone and non propulsive rhthmic contractions
used to antagonize the spasmogenic actions of morphine and potentiate anti propulsive activity
atropine
morphine A, D, M, E
readily absorbed from GI or nasal mucosa or lungs, injection availabe via skin, muscle, or venous routes
penetrates CNS poorly, compared to heroin
does not accumulate in tissues and has short half life (4 hrs)
conjugated with glucuronic acid in liver
elimination depends on metabolism, excreted by urine 90%, 10% biliary
pinpoint pupils
depressed respiration
BP fall
low body temp
flaccid skeletal muscle
possible convulsion
symptoms of acute morphine poisoning
symptoms of acute morphine posioning
pinpoint pupils
depressed respiration
BP fall
low body temp
flaccid skeletal muscle
possible convulsion
treatment of acute morphine poisoning
ventilation
repeated injections of nalaxone (antagonist)
tolerance to morphine is
pharmacodynamic
withdrawel from morphine is better or worse than that from ethanol and barb
leess severe
slowly demethylated to morphone
absorbed better (affective orally and parenterally)
codeine
phenylpiperidine derivitive
meperidine
diphenoxylate
in equianalgesic doses, less spasmogenic, less constipation, and less urine retention than morphine
meperidine
preferred opiate for obstetrical analgesia
meperidine
meperidine
phyilpiperidine derivitive
hydrolized to meperidinic acid
conjugated in liver to normeperine and exerts excitatory affects
used in the treatment of diarhea with atropine
virtually insoluble
little abuse potential
no perceptible CNS effects in theraputic range
diphenoxylate
80 times more potent than morphine
used in combo with droperidol
fentanyl
superior to morphone in most ways, oral abs, larger T1/2 (15 hrs), less withdrawel, ident pharm,
used for opiate addiction replacement therapy
methadone
prescribed in lieu of codeine
less effective
propoxyphene
depot opiate
produces methadone
used in treatment of addiction
1 acetylmethadol
powerful kappa agonist
analgesic = morphine
resp dep < morhphine
dysphoria > morphine
pentazocin
low abuse liability
antagonist of morphine
naloxone
naltrexone
naloxone
antagonist of opioids
zero bioavailablity orally IV short T1/2
dextromethorphan
no analgesic potency
antitussive
very minimal toxicity
clonidine
reduces the adversive quality of withdrawal from opiate
may reduce craving
criteria for opioid choice
type of pain
required duration of action
intensity of pain
long acting opioid
methadone, morphine, oxymorphone
short acting opioid
meperidine
used for low to moderate pain
oral codeine
or low doses of oxcodon or hydrocodone + aspirin
used for intense pain
NSAIDS morphine
oxymorphone iv or sc
intrathecal opiates

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