Small animal - opioids Flashcards
what are 6 opioids used in SA?
- buprenorphine
- butorphanol
- fentanyl
- morphine
- hydromorphone
- methadone
what is the dose of buprenorphine (IM, SQ, IV, OTM)?
0.01 - 0.04 mg/kg
what is the dose of butorphanol (IM, SQ, IV)?
0.2 - 0.8mg/kg
what is the dose of fentanyl (IM, SQ, IV)?
0.002-0.01mg/kg
what is the dose of morphine (IM, SQ, IV)?
0.1 - 1mg/kg
what is the dose of hydromorphone (IM, SQ, IV)?
0.05 - 0.2 mg/kg
what is the dose of methadone (IM, SQ, IV)?
0.1 - 0.7 mg/kg
what effects do mu opioids produce in SA?
analgesic, euphorigenic, respiratory depression, miosis, possible vasodilation effects
full opioid agonists MOA
- activate mu receptors
- Increasing doses of full agonists produce increasing effects until a maximum effect is reached OR the receptor is fully activated.
- Opioids with the greatest abuse potential are full agonists (e.g., morphine, heroin, methadone, oxycodone, hydromorphone
opioid antagonist MOA
- bind to and effectively block opioid receptors
- prevent receptors from being activated by agonist compounds
- Examples of opioid antagonists are naltrexone and naloxone.
partial opioid agonist MOA
- Partial agonists bind to receptors and activate them, but not to the same degree as do full agonists
- At lower doses and in individuals who are not dependent on opioids, full agonists and partial agonists produce effects that are indistinguishable
- As doses are increased, both full and partial agonists produce increasing effects
- At a certain point, however, the increasing effects of partial agonists reach maximum levels and DO NOT increase further, even if doses continue to rise—the ceiling effect.
- As higher doses are reached, partial agonists can act like antagonists—occupying receptors but not activating them (or only partially activating them), while at the same time displacing or blocking full agonists from receptors.
What are the partial mu agonist drugs?
- buprenorphine
What are the full mu agonist drugs?
- fentanyl
- morphine
- hydromorphone
- methadone
What are the mu antagonist drugs?
- butorphanol (also a kappa agonist)
disadvantages of buprenorphine - 3
- Since it has such a strong affinity for mu receptors, if buprenorphine is used
in conjunction with another mu agonist, the effects of buprenorphine will generally prevail. - reversal = Because of its affinity for its receptors, it is difficult to antagonize the effects with naloxone
- The bioavailability of OTM route in dogs is much lower than in cats, so considerably higher doses may
be necessary
function of kappa agonist
- analgesia
- anticonvulsant
- depression
- dysphoria
- diuresis
- sedation
- miosis
advantages of butorphanol
- kappa agonist, mu antagonist
- moderate visceral analgesia
- potentiates the action of other anesthetic agents
- DOA very short in dogs (< 1hr) and moderate in cats (2-6 hr)
- can be used to
partially reverse the narcosis produced by pure mu agonists (fentanyl, hydromorphone, etc) - reversal = naloxone
disadvantages of butorphanol - 3
- produces sedation when used in CONJUNCTION with tranquilizer
- no MAC reduction
- not as effective for severe pain
advantages of fentanyl - 6
- mild sedation
- good analgesia
- doesn’t usually cause vomiting or defecation
- CV changes minimal (causes bradycardia - Tx’d with anticholinergic)
- decreases MAC without causing hypotension
- reversal = naloxone
disadvantages of fentanyl -
- dose-dependent decrease in tidal volume with CO2 increase - can last several hours
disadvantages of fentanyl -
- dose-dependent decrease in tidal volume with CO2 increase - can last several hours
- ataxia and exaggerated response to loud noises - NOT for use in young pts
- profound bradycardia - atropine responsive
- dysphoria and excitement in CATS = no induction in this sp
- short DOA (<30min)
advantages of morphine - 5
- inexpensive
- good sedation (dogs)
- neuroleptanalgesic (used with acepromazine) in dogs and cats
- DOA long lasting (up to 6hr) = good ANALGESIA
- great for post-op analgesia
disadvantages of morphine - 6
- dose dependent excitement (cats)
- bradycardia (Tx = atropine)
- resp depression (severe at high doses)
- contracture of sphincter of Oddi (CONTRAINDICATED in biliary stasis)
- VOMITING and defecation (premed)
- IV admin = histamine release causing CV collapse = ADMIN SLOWLY
advantages of hydromorphone - 3
- DOA 2-4hrs
- preferred over morphine in cats
- can be given IV - NO histamine release
disadvantages of hydromophone - 4
- resp depression
- bradycardia
- VOMITING - reduced by IV admin
- post-anesthetic HYPERthermia in cats (monitor several hours after)
advantages of methadone
1.
advantages of methadone
- major advantage over morphine and hydro = LESS likely to cause VOMITING as a premed
disadvantages of methadone
- bradycardia
- resp depression
- expensive
