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kyleannkelsey
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What receptor do these drugs work at and what structure indicates this?
- Pentacyclic
- “Antagonism”
- Mu antagonists:
- N-allyl or N-cyclopropylmethyl on the nitrogen atom
- 7,8 dihydro-6-one
- 14 B-OH
- (Naloxone and Naltrexone)
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By what mechanism do these drugs cause high affinity mu antagonism?
- Induce conformational changes that uncouples the receptors from their G-proteins
- (Naloxone and Naltrexone)
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If you had a patient on a mu agonist,what considerations would need to be made prior to staring one of these drugs?
- To prevent withdrawal:
- Must be agonist free for 7-10 days before one of these antagonists can be administered
- Unless trying to rescue a patient from fatal overdose (Ggive STAT)
- (Naloxone and Naltrexone)
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How does the potency of these two drugs compare?
- Naltrexone is twice as potent as naloxone
- Due to an enhanced lipophilicity of Naltrexone and distribution to CNS
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Is this drug orally active?
Yes
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Why is this drug useful for opioid addiction therapy?
- Mu antagonist
- Blocks opioid receptors in opioid-free patients = thwarts euphoria of agonists if patient relapses
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(True/False) Naltrexone has shown efficacy in the treatment of alcoholism.
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Low doses (4.5 mg daily) naltrexone has shown efficacy in what ailment?
Bowel ulcerations and enhancing immunity in active Crohn’s disease
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Why would you choose an IM version over an oral version of Naltrexone for opioid addiction therapy?
- IM contains a slow release polymer that makes it last for 4 weeks
- Increases convenience and adherence
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How would the daily exposure to Naltrexone compare between an IM Q4weeks and a 50 mg tablet QD and why?
- Greater exposure with the IM version
- Avoids 1st pass metabolism so: Much less metabolite is formed IM
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What is the primary metabolite of this drug and what enzyme produces it?
 - 6B-naltrexo
- Cytosolic enzyme dihydrodiol dehydrogenase
- (Naltrexone)
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is this drug orally active?
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Why is this drug not orally active?
- Due to inactivating pre-hepatic and first pass metabolism
- Allyl group is oxidized and conjugated
- (Naloxone)
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What is the primary urinary metabolite of this drug?
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In what form is this drug available?
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What is this drug used for?
- Reverse life-threatening opioid overdose, respiratory and CNS depression
- (Naloxone)
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Will this drug precipitate withdrawal in mu agonist users?
- Yes, mu Antagonist
- (Naloxone)
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Why will symptom of withdrawal be short lived when this drug is given to a mu agonist user?
- 1-2 hour half-life
- (Naloxone)
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What was this drug used for?
- IV use in reversing life-threatening opioid overdose
- Mu antagonist
- (nalmefene)
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Why was this drug likely taken off the market?
- Excessively long DOA (11 hours) to be used for reversing opioid overdose
- Caused prolonged withdrawal symptoms
- (nalmefene)
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Is this drug orally active?
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Why does this drug have such a long half life (11 hours)?
 - High affinity binding as a mu antagonist due to the 6-exocyclic methylene moiety
- (nalmefene)
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Other than treating life threatening overdose, what other uses could this drug have due to its long half life and high oral bioavailability?
- Preventing relapse in recovering alcoholics
- Blocking mu agonist effects of fentanyl
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