Narcotics Flashcards
What type of receptor is the opioid receptors?
GPCR
Effect of opioid receptor
decreased adenyl cyclase, Ca2+ channel activity
increase K+ channel activity
(hyperpolarizes)
What is the main opioid receptor targeted by analgesics?
u (Mu)
Describe morphine’s structure and sites that account for variation
5 ring structure
modifications at positions 3,6, and 17
What do opioid receptor agonists do?
Inhibit the release of substance P and ascending transmission of pain from dorsal horn neurons.
Possible mechanism of tolerance?
internalization/ phosphorylation of receptors
What two side effects do patient’s on opioids exhibit little tolerance to?
Miosis and constipation
What are the SE of opioids?
Miosis, constipation, respiratory depression
N/V, uticaria, bad dreams, sedation, delirium, Seizures, urinary retention
Where and how are opioids metaboilized?
Liver, conjugation w/ glucoronic acid
Why is the Cmax for oral opioids lower than IV?
first pass metabolism
How do you address the bolus effect of IV/IM dosing?
Consider CI or extended release oral formulations
Why are opioids often used in with adjuvants?
To reduce the necessary dose, decreasing unwanted SE.
When are opioids used?
To treat moderate or severe pain.
What metabolite of morphine is the most active/ highest potency?
M-6- glucuronide
What is morphine’s MOA?
Mu- opioid receptor agonist
What are the effects of morphine?
severe analgesia, mood alteration, antitussive, sedation
What pathway is responsible for conversion of 10% of codeine into morphine?
CYP2D6
What are the effects of codeine?
moderate analgesia, antitussive
What is codeine’s MOA?
Mu- opioid receptor agonist
What concern is there for codeine use in Caucasians?
10% can’t convert to morphine, but still experience SE
How does tramadol work?
weak Mu receptor agonist, inhibition of NE/5HT uptake
What are the effects of tramadol?
moderate analgesia
What are the effects of fentanyl?
severe analgesia
How is fentanyl delivered?
IV or transdermal
How long should you wait before increasing the does of fentanyl?
1 week
What is MOA of fentanyl?
Mu-opioid receptor agonist, highly lipid soluble
What is the MOA of methadone, oxycodone, and meperidine?
Mu-opioid receptor agonist
What is methadone used to treat?
chronic severe pain
treatment of heroine and opioid addicts
When initially treating with methadone, what precautions should be taken?
Do not raise dose more than 1/ wk
Overdose common in initial treatment
What is oxycodone used to treat?
moderate to severe analgesia
What two opioids are no longer used?
Meperidine and Propoxyphene
What are Loperamide (Imodium) and Diphenoxylate (Lomotil) used to treat?
DIarrhea
Loperamide (Imodium) and Diphenoxylate (Lomotil) MOA?
slows peristalsis by binding opioid receptors in intestine, possibly decreases GI secretions
What is Naloxone (Narcan) used to treat?
opioid toxicity
Naloxone (Narcan) MOA?
competitive mu, delta, and kappa opioid receptor antagonist
SE of Naloxone?
can precipitate withdrawal
N/V/D, piloerection, yawning, irritabilty
What is Naltrexone (Revia) used to treat?
Alcoholism
SE of Naltrexone?
prolonged withdrawal- N/V, piloerection, yawning
MOA of Naltrexone (Revia)?
Mu-opioid receptor antagonist
What must you be cautious of when prescribing a opioid in combination with acetaminophen?
At home, OTC use. Risk of overdose
How long between doses for oral immediate release preparations vs extended release preparations?
immediate- every 4 hours
extended- 8-24 hrs
What should you not use to treat breakthrough dosing?
extended release opioids
What should you do if pain is poorly responsive to opioids?
Try alternative route or rotate opioid
Try coanalgesic
What must be kept in mind when changing drugs or route?
Equianalgesic dosing
When changing drug or route, decrease equianalgesic dose by 25-50% at first to avoid bad SE
What should be done to avoid constipation w/ opioid use?
Prescribe stool softener w/ stimulant laxative at the same time you start opioid.
If respiratory depression begins in a patient taking opioids, what should you do?
Give IV Naloxone (Narcan)
How do you decrease risk of delirium in patient being treated with opioids?
Confirm normal liver (metabolism) / kidney (excretion) function
