Opioids Flashcards
3 Main Types of Opioid Receptors
1) mu
2) kappa
3) delta
Clinically used opioids mostly act on what two types of receptors?
kappa and mu
Which type of opioid med is the most effective but also has the most side effects?
full mu agonists
Do opioids have the same effect in all species?
NO - there are species differences in receptor distributions
3 Locations of Opioid Receptors
brain
spinal cord
periphery
Opioids and MAC
opioids reduce MAC so reduces inhalant requirements –> better for CV system
Why do healthy, agitated horses sometimes have an excitatory response to opioids?
lots of mu receptors in the cortex
Opioids and Bulldogs
can cause panting, so caution must be used in brachycephalics and lar-pars (hydromorphone)
Antitussive Opioids
butorphanol, hydrocodone
How are opioids considered an emetic and an anti-emetic?
stimulates vomiting at CRTZ outside the brain but suppresses the vomiting center within the BBB (just takes a while to get there)
Opioid Effect on GI Motility
DECERASES motility/propulsive contractions, increases segmental
ex: Imodium!
What type of opioid should be used for endoscopy?
kappa agonist (butorphanol)
mu agonists will tighten sphincters?/make it difficult to pass scope
Effect of Opioids on Body Temp in Dogs vs Cats
HYPOthermia in dogs (mild)
HYPERthermia in cats (can be quite marked)
mydriasis
pupil dilation; occurs with opioid administration in cats, horses, ruminants
miosis
pupil constriction; occurs with opioid administration in dogs, rabbits, rats
What is the only opioid NOT metabolized by the liver?
REMIFENTANIL
metabolized by plasma esterases, so good for patients with severe liver dz
opioid excretion
urine and feces (water soluble)
4 Full Mu (u) Agonists in Vet Med
Morphine
Hydromorphone
Methadone
Fentanyl
Why is morphine used in epidurals?
it is the LEAST lipid soluble (so it stays where you put it)
(also bonus, it’s inexpensive)
Undesirable Side Effects of Hydromorphone
vomiting and panting (remember not good for bulldogs)
Why is methadone awesome?
MULTIMODAL ANALGESIA (mu agonist, NMDA antagonist, SSRI type thing)
plus minimal vomiting or panting, less dysphoria
Why is methadone not awesome?
it’s hella expensive
How is fentanyl different than your other full mu agonists?
very short duration of action (needs CRI)
Buprenorphine
partial mu agonist AND kappa antagonist
Butorphanol (Torb)
partial mu antagonist AND kappa agonist
short duration, good sedation, but minimal analgesia
Naloxone
antagonist at all receptors, used in overdose situations or opioid dysphoria (titrated to effect)
