Lecture 3 8/27/24 Flashcards
What are the main reasons to use opioids?
-mainstay of analgesia
-drug/species dependent sedative effects
What are the synergistic effects of opioids when combined with a major sedative?
-more profound sedation
-more profound analgesia
What is the mechanism of action for opioids?
binds to mu, kappa, and/or delta opioid receptors, generally resulting in inhibition
What are the classifications of opioids based on receptor selectivity?
-pure mu agonist
-partial mu agonist
-mixed agonist/antagonist
How does a mixed agonist/antagonist work?
-agonist at the kappa receptor
-antagonist at the mu receptor
-activates kappa receptor to inhibit pain
What are the characteristics of pure mu agonists?
-profound analgesia
-moderate sedation
Which opioids fall into the pure mu agonist category?
-morphine
-meperidine
-hydromorphone
-oxymorphine
-methadone
-fentanyl
-remifentanil
What are the characteristics of partial mu agonists?
-moderate analgesia
-minimal sedation
Which opioid is the main drug in the partial mu agonist category?
buprenorphine
What are the characteristics of kappa agonists/mu antagonists?
-mild analgesia for visceral pain only
-moderate sedation
Which opioid is the main drug in the kappa agonist/mu antagonist category?
butorphanol
At which locations do opioids function?
-brain
-spinal cord
-peripheral nociceptors
-joints
-immune cells
What are the routes of administration for opioids?
-IV
-IM
-epidural
-oral/transmucosal
-transdermal
What are the opioid side effects seen at the CNS level?
-analgesia
-sedation
-dysphoria/possible euphoria
-increased locomotor activity
What is the opioid side effect seen at the respiratory level?
dose-dependent respiratory depression
Which species must be carefully monitored for resp. depression when using opioids?
primates and rabbits
What is the opioid side effect seen at the cardiovascular level?
drug-dependent, vagally mediated bradycardia
Which opioid is most associated with bradycardia side effects?
methadone
Which drugs are used to treat opioid-induced bradycardia?
-atropine
-glyco
What are the opioid side effects seen at the GI level?
-ileus/constipation
-nausea and vomiting
How do opioids affect temperature regulation in cats?
all opioids lead to hyperthermia in cats
What are the characteristics of opioid-induced histamine release?
-primarily associated with morphine
-seen most commonly with fast IV administration
-can lead to hypotension, tachycardia, and urticaria
Which opioids are at greatest risk for diversion/inappropriate use by people?
pure mu agonists, which are schedule II
What are the characteristics of morphine?
-duration of action around 2-4 hours
-most common side effects are vomiting and histamine release
-full mu agonist
What are the characteristics of meperidine?
-duration of action around 1 hour
-most common side effects are vomiting, histamine release, and anti-cholinergic effects (increased heart rate)
-full mu agonist
What are the characteristics of hydromorphone?
-duration of action around 4-6 hours
-most common side effects are panting and vomiting
-full mu agonist
What are the characteristics of methadone?
-duration of action around 2-4 hours
-NMDA antagonist/good for wind-up/chronic pain
-most common side effect is profound bradycardia
-full mu agonist
What are the characteristics of fentanyl?
-duration of action around 30 minutes
-given as a CRI or transdermal patch to increase duration
-also given oral/transmucosal
-full mu agonist
What are the characteristics of remifentanil?
-duration of action around 3-5 minutes
-given as a CRI to increase duration
-metabolized by plasma esterases; safe for the liver
-full mu agonist
What are the characteristics of thiafentanil, carfentanil, and etorpine?
-very potent!!
-small volumes used for immobilization of large zoo species
-PPE must be used
-must have reversal agent readily available
-full mu agonists
What are the characteristics of buprenorphine?
-partial mu agonist
-duration of action around 6-8 hours
-given oral/transmucosal
-difficult to reverse
-adverse effects are mild
What are the characteristics of simbadol?
-concentrated buprenorphine
-duration of action around 24 hours
-licensed for cats
-given SQ
What are the characteristics of transdermal buprenorphine?
-licensed for cats
-up to 96 hours of analgesia
-must be applied 2 hours prior to painful stimulus
-less crazy side effects compared to simbadol
What are the characteristics of butorphanol?
-mixed kappa agonist and mu antagonist
-duration of action around 1 hour
-mild adverse effects
-kappa agonism causes sedation
-act as reversal agents for full mu agonists
What are the characteristics of naloxone?
-opioid antagonist
-duration of action around 20-30 minutes
-may need to be given multiple times for opioids with longer durations of action
What are the characteristics of naltrexone/nalmefene?
-opioid antagonists
-longer duration of action
-used in wildlife/zoo species that cannot be monitored closely enough to use naloxone
