Pain Therapies Flashcards
What are the most common administration forms of acute and chronic pain relievers?
ACUTE: injectable, OTM, topical, oral
CHRONIC: oral, OTM, topical, injectable
What are the 4 classic agents used to prevent and treat acute pain?
- opioids
- alpha-2 agonists
- anti-inflammatories
- local anesthetics
What is the difference between opium, opiates, and opioids?
OPIUM = substance derived from the poppy, Papaver sommiferum
OPIATE = drugs derived naturally from opium, like morphine and codeine
OPIOID = exogenous substances, natural and synthetic, that bind to endogenous receptor systems
What is morphine?
one of twenty natural alkaloids in opium
What is Simbadol? What are 3 major benefits?
buprenorphine injection - Schedule III
- post-op pain control day and night for patient
- proven efficacy in cats
- multidose vial available
What is Recuvrya? When is it indicated for use?
transdermal fentanyl solution approved for use in dogs
control of post-op pain associated with moderate to severely painful surgical procedures —> apply 2-4 hours before sx to allow peak plasma concentrations 12-14 hrs later
What is tramadol? What is responsible for its effects?
analgesic and antitussive weak mu partial agonist that inhibits serotonin and norepinephrine uptake and has alpha-2 agonist-like effects
metabolite M1 = analgesia
What are 6 oral opioid alternatives?
- codeine
- tylenol*
- hydrocodone
- oxycodone
- morphine (ER)
- methadone (cats only)
What side effect is associated with codeine use in dogs? What is it commonly combined with?
constipation
tylenol
What are the 4 locations of endogenous opioid receptors? What are the 3 types of receptors?
- dorsal horn of the spinal cord
- brain
- peripheral nervous system
- non-nervous tissue: GIT, CV system, endorine system
mu, kappa, delta
What substances to opioid receptors commonly interact with?
endorphins, enkephalins, dynorphins
What are 6 common effects associated with mu receptor agonism?
- respiratory depression
- euphoria
- addiction
- analgesia
- sedation
- miosis
What are 4 common effects associated with kappa receptor agonism?
- analgesia
- sedation
- respiratory depression
- miosis
What 2 effects are associated with delta receptor agonism?
- analgesia
- motor dysfunction
Opioid receptor effects, agonists, and antagonists:
What opioids are considered agonists? Partial agonists?
morphine, codeine, fentanyl, meperidine, hydo/oxycodone, etorphine
buprenorphine
What opioids are considered antagonists? Mixed agonist/antagonist?
naloxone, naltrexone
butorphanol
What happens when opioid receptors are activated?
G-coupled protein receptors catalyze the intracellular formation of second messengers
What do G-proteins couple? What 3 subunits are present?
- cell surface receptors to catalytic units
- receptor to ion channels
alpha, beta, gamma
What 3 effects do G-proteins have once they opioid receptor is agonized?
- inhibits cAMP
- inhibits voltage-gated Ca and Na channels, resulting in decreased calcium influx, calcium intracellular modulation, and neurotransmitter release
- increased K conductance, resulting in hyperpolarization of cells and lessened nerve impulse transmission
What are the 6 primary clinical effects of opioids? What is seen in cats?
- analgesia
- sedation
- bradycardia
- panting
- respiratory depression
- ileus, urinary retention
hyperthermia - hydromorphone, buprenorphine
What action of opioids causes analgesia? What are the best opioids for analgesia?
inhibits pain transmission in the dorsal horn of the spinal cord at mu receptors (pure mu agonists > mixed, partial)
fentanyl, morphine, hydro/oxymorphone, sufentanil
What are the 4 routes used to deliver opioids? What is avoided?
- parenteral**
- epidural
- spinal
- local
oral - first-pass metabolism (tramadol)
What are the 3 most potent pure mur agonists?
- carfentanil
- etorphine
- fentanyl
What opioid gives the best pain relief?
fentanyl
(buprenorphine is a good option in cats)
What opioid gives the best sedation?
butorphanol
What 3 respiratory effects do opioids have?
- decrease tidal volume and rate
- decrease responsiveness of respiratory center to CO2
- panting due to direct effect on temperature regulating center
In what 2 situations are the respiratory effects of opioids particularly noticeable?
- combined with other agents, like Acepromazine and Medetomidine
- “higher” fentanyls used IV, like carfentanil, remifentanil, sufentanyl
ventilation may be required!
What 3 opioids have anti-tussive effects?
- codeine
- hydrocodone
- butorphanol
What 3 effects do opioids have on the CV system?
- cardio soothing - CO and contractility maintained
- increased vagal tone - mild bradycardia, heart block
- histamine release - vasodilation
What 2 opioids are associated with histamine release?
- morphine
- meperidine
(vasodilation!)
How do opioids affect pupil dilation in the eyes of dogs and cats?
DOG = miosis
CAT = mydriasis
In what patients is mild sedation most commonly seen with the use of opioids?
painful animals
- non-painful = excitement, most commonly in cats and horses
What GI effects are associated with opioid use?
- initial increase in peristalsis
- GI stasis —> vomiting, nausea, constipation
What 4 effects are associated with continuous use of opioids?
- opioid hyperalgesia (monotherapy)
- increased inflammation
- tumor metastasis and angiogenesis
- cardiac autonomic non-responsiveness
What antiemetics are commonly coupled with opioids? In what 2 is this not necessary?
- neurokinin antagonist (Maopitant)
- metoclopramide
- ondansetron
oxymorphone and methadone
In what patients should opioids be used carefully?
- pre-existing CNS depression
- pre-existing respiratory depression
What full reversals are used for opioids? Partial reversal?
naloxone, naltexone
butorphanol
How do opioid reversals compare to alpha-2 reversals? Why do we use reversals?
very short-lived —> animals often “renarcotize”
- emergency overdose
- reduce narcosis
- rouse an animal from too much sedation
What are some pros to using butorphanol?
- minimal opioid side effects
- respiratory depression
- urinary retention
- vomiting
- great antiemetic
- GI analgesic in cats and horses
- very safe
- can act as a benign filler in premeds
- minimal expense