Small animal - opioids

Question 1

what are 6 opioids used in SA?

Answer 1

1. buprenorphine
2. butorphanol
3. fentanyl
4. morphine
5. hydromorphone
6. methadone

Question 2

what is the dose of buprenorphine (IM, SQ, IV, OTM)?

Answer 2

0.01 - 0.04 mg/kg

Question 3

what is the dose of butorphanol (IM, SQ, IV)?

Answer 3

0.2 - 0.8mg/kg

Question 4

what is the dose of fentanyl (IM, SQ, IV)?

Answer 4

0.002-0.01mg/kg

Question 5

what is the dose of morphine (IM, SQ, IV)?

Answer 5

0.1 - 1mg/kg

Question 6

what is the dose of hydromorphone (IM, SQ, IV)?

Answer 6

0.05 - 0.2 mg/kg

Question 7

what is the dose of methadone (IM, SQ, IV)?

Answer 7

0.1 - 0.7 mg/kg

Question 8

what effects do mu opioids produce in SA?

Answer 8

analgesic, euphorigenic, respiratory depression, miosis, possible vasodilation effects

Question 9

full opioid agonists MOA

Answer 9

• 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

Question 10

opioid antagonist MOA

Answer 10

• bind to and effectively block opioid receptors
• prevent receptors from being activated by agonist compounds
• Examples of opioid antagonists are naltrexone and naloxone.

Question 11

partial opioid agonist MOA

Answer 11

• 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.

Question 12

What are the partial mu agonist drugs?

Answer 12

1. buprenorphine

Question 13

What are the full mu agonist drugs?

Answer 13

1. fentanyl
2. morphine
3. hydromorphone
4. methadone

Question 14

What are the mu antagonist drugs?

Answer 14

1. butorphanol (also a kappa agonist)

Question 15

disadvantages of buprenorphine - 3

Answer 15

1. 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.
2. reversal = Because of its affinity for its receptors, it is difficult to antagonize the effects with naloxone
3. The bioavailability of OTM route in dogs is much lower than in cats, so considerably higher doses may
   be necessary

Question 16

function of kappa agonist

Answer 16

1. analgesia
2. anticonvulsant
3. depression
4. dysphoria
5. diuresis
6. sedation
7. miosis

Question 17

advantages of butorphanol

Answer 17

1. kappa agonist, mu antagonist
2. moderate visceral analgesia
3. potentiates the action of other anesthetic agents
4. DOA very short in dogs (< 1hr) and moderate in cats (2-6 hr)
5. can be used to
   partially reverse the narcosis produced by pure mu agonists (fentanyl, hydromorphone, etc)
6. reversal = naloxone

Question 18

disadvantages of butorphanol - 3

Answer 18

1. produces sedation when used in CONJUNCTION with tranquilizer
2. no MAC reduction
3. not as effective for severe pain

Question 19

advantages of fentanyl - 6

Answer 19

1. mild sedation
2. good analgesia
3. doesn’t usually cause vomiting or defecation
4. CV changes minimal (causes bradycardia - Tx’d with anticholinergic)
5. decreases MAC without causing hypotension
6. reversal = naloxone

Question 20

disadvantages of fentanyl -

Answer 20

1. dose-dependent decrease in tidal volume with CO2 increase - can last several hours

Question 21

disadvantages of fentanyl -

Answer 21

1. dose-dependent decrease in tidal volume with CO2 increase - can last several hours
2. ataxia and exaggerated response to loud noises - NOT for use in young pts
3. profound bradycardia - atropine responsive
4. dysphoria and excitement in CATS = no induction in this sp
5. short DOA (<30min)

Question 22

advantages of morphine - 5

Answer 22

1. inexpensive
2. good sedation (dogs)
3. neuroleptanalgesic (used with acepromazine) in dogs and cats
4. DOA long lasting (up to 6hr) = good ANALGESIA
5. great for post-op analgesia

Question 23

disadvantages of morphine - 6

Answer 23

1. dose dependent excitement (cats)
2. bradycardia (Tx = atropine)
3. resp depression (severe at high doses)
4. contracture of sphincter of Oddi (CONTRAINDICATED in biliary stasis)
5. VOMITING and defecation (premed)
6. IV admin = histamine release causing CV collapse = ADMIN SLOWLY

Question 24

advantages of hydromorphone - 3

Answer 24

1. DOA 2-4hrs
2. preferred over morphine in cats
3. can be given IV - NO histamine release

Question 25

disadvantages of hydromophone - 4

Answer 25

1. resp depression
2. bradycardia
3. VOMITING - reduced by IV admin
4. post-anesthetic HYPERthermia in cats (monitor several hours after)

Question 26

advantages of methadone

Answer 26

1.

Question 27

advantages of methadone

Answer 27

1. major advantage over morphine and hydro = LESS likely to cause VOMITING as a premed

Question 28

disadvantages of methadone

Answer 28

1. bradycardia
2. resp depression
3. expensive