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32 Cards in this Set
- Front
- Back
presynaptic vs. post synaptic action of opioids
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presynaptic: Gi activation to decrease cAMp and therefore NT release (closure of Ca channels)
postsynaptic: open K channels to cause hyperolarization |
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CNS effects of morphine: analgesia
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analgesia
-selectively interferes with nocioception, affective reaction; inhibits conduction; action mediated via receptors on the dorsal horn of the spinal cord, PAG, dorsal raphe nuclei, limbic regions |
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CNS fx of morphine other than analgesia
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behavioral fx: dysphoria then euphoria
sedation emetic d/t direct stimulation of CTZ (chronic inhibits) antitussive (direct action on medulla) resp depression d/t dec sensitivity to CO2= dec rate and depth of respiration hypothalamus: decreased body temp, ACTH, FSH, LH, TSH miosis trunchial rigidity d/t increased tone to spinal motoneurons |
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peripheral actions of morphine
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GI tract- inc tone and dec peristalsis
biliary tract- gall bladder or bile duct spasm d/t increased biliary pressure urinary tract increased muscle tone= decreased urinary output CV: peripheral VD and orthostatic HTN; dose-dependent bradycardia cerebral vasodilation, increased CSF pressure indirect: histamine release-> itching, sweating, redness of eyes; bronchoconstriction and decreased secretions |
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opiods and the placenta and fetus
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crosses placenta
fetal BBB not developed and baby is dependent |
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mechanism of opioid elimination
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rapidly conjugated with glucuronide in liver- significant first pass fx
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pharmacogenetics: codeine and anesthesia
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codeine must be metabolized to morphine by Cyt 2D6 to be active
7% of caucasions lack this and will have no benefit |
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tolerance to opioids
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marked: to depressant actions
little: stimulating actions |
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how does tolerance develop? what is it related to/
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probably due to activity of adnylyl cyclase and receptor downregulation
degree of tolerance is related to : dose, frequency, exposure, duration of drug use |
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cross tolerance occurs among__________ but not ________
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opioids but not other CNS depressants
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what is the significance of cross-dependence?
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can give another opioid to someone addicted
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what are the effects that have minimal or no tolerance?
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miosis
constipation convulsions antagonist actions |
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does tolerance develop to bradycardia?
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moderate tolerance
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primary contraindications to opioid use
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asthma
emphysema liver damage head injuries acute alcohol use previous addiction convulsive disorders abdominal pain of unknown origin |
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types of drugs that opioids interact with
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meperidine + MAOI can cause serotonin syndrome
methadone may cause torsades: careful with antiarrhythmics depressant fx will be worsened with CNS depressants: phenothiazines, MAOI, TCA, cimetidine amphetidine may enhance fx |
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what is acute pure opioid OD and how do you treat it?
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triad: coma, pinpoint pupils, respiratory depression
tx: maintain respiration, give opioid antagonist, preferably naloxone |
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what is the primary cause of death from opioid overdose
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respiratory failure
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what is the rationale of using methadone to treat opiate-dependent individuals?
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affects mu receptors
tolerance develops more slowly withdrawal is long and mild inverse relationship of half life to intensity of WDS cheap |
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indicate which opioid receptors are associated with:
analgesia euphoria miosis dysphoria physical dependence respiratory depression |
mu (μ) – euphoria, analgesia, physical dependence, respiratory depression
kappa (κ) – miosis, analgesia of pentazocine, sedation, dysphoria delta (δ) similar to μ receptors, enkephalins natural agonists; mediate neuro-endocrine effects N/OFQ (pro-orphanin) – newest opioid receptor; orphanin natural agonists |
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Distinguish between morphine, pentazocine and naloxone with respect to their actions at the µ receptor.
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morphine: agonist
pentazocine: pAg naloxone: antagonist |
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what is the primary difference between naloxone and naltrexone?
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naloxone is only parenterally effective
naltrexone is orally effective and longer lasting; can also be given as a monthly IM injection |
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Compare the intensity of withdrawal syndrome from methadone when a patient stops taking the drug versus the intensity if precipitated by naloxone administration.
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methadone: mild
naloxone: causes immediate severe WDS |
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which opioid analgesic is most likely to produce a serotonin syndrome if used in combo with monoamine oxidase inhibitors
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meperidine
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main difference between fentanyl and morphine
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short duration, much more powerful
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Indicate what unique pharmacokinetic aspects of remifentanil make it more useful for infusion anesthesia than the other meperidine congeners.
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ultra short duration due to metabolism and small Vd rather than redistribution
unique: rapidly metabolized by tissues and blood esterases to give it an extremely short half life and can have a titration of dose effect during anesthesia |
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tolerance, physical dependence and withdrawal
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tolerance and physical dependence are directly related
greater PD; greater intensity of WDS |
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what is the primary effect of morphine and most opioids on the heart
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CV system: peripheral VD and orthostatic hypotension as a result of CNS actions and histamine release
dose-dependent bradycardia (increased PNS and decreased SNS) |
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risk of death: opioid withdrawal vs. alcohol/barbiturate withdrawal
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death can happen with alcohol or barbiturates
not with opioids |
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which opioid is least likely to
1) produce constipation 2)suppress cough |
1) meperidine, codeine
2) meperidine |
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what are the acitve metabolites of morphine and meperidine and what are the potential benefits or risks associated with each one?
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morphine 6 glucuronide contributes to analgesia
morphine 3 glucuronide causes dysphoric fx meperidine: metabolite normeperidine is a stimulant and can cause seizures with accumulation |
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analgesic potency: morphine, meperidine, fentanyl
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fentanyl>morphine>meperidine
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use, moa of methylnaltrexone and alvimopan
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both are antagonists
methylnaltrexone: reverses opioid-induced constipation but not analgesia (no CNS fx) alvimopan is for post-op ileus, given before and after bowel resection (stays in GI tract) |