Opioids

Question 1

Butorphanol

Answer 1

-partial agonist
-used to reverse opioid mediated sedation or respiratory depression
-it is a mu antagonist
-kappa agonist - not as good for sedation and respiratory depression
therefore it maintains analgesia through the kappa receptor
-very expensive
-quality of analgesia depends on quality of pain - if visceral then low quality of pain so not great for spays
-side effects include excitement

Question 2

which drugs are mu agonists

Answer 2

• morphine
• oxymorphine (not made any more)
• fentanyl
• remidentanil
• hydromorphone

Question 3

morphine

Answer 3

• very effective analgesic - most highly used
• less lipid soluble then others so crosses BBB slower and lasts longer
• it is metabolized to morphine-6-glucuronide (causes analgesia) and morphine-3-glucuronide (little analgesia, responsible for excitement)
• good analgesia 4-6hours after IM
• IV: histamine release and hypotension
• medium expensiveness
• not often used in horses because of its price

Question 4

Oxymorphine

Answer 4

• IV: no histamine release
• sedation
• respiration depression
• good CV stability
• doesnt last as long
• least amount of dysphoria
• very expensive and no longer available

Question 5

Hydromorphone

Answer 5

• IV: no histamine release but some excitement (cats)
• good CV stability. still get bradycardia
• more sedation than oxymorphine
• lots of dysphoria and lasts 2-3 hours IM
• relatively cheap
• dogs will vomit so can give them acepromazine to counteract it
• resp depression

Question 6

Fentanyl

Answer 6

• very good analgesia
• IV: takes 20-30 min
• can be given CRI or in patch form
• good CV stability
• lots of respiratory depression
• moderately expensive but very expensive in horses because need to use so much

Question 7

remifentanyl

Answer 7

• equally efficacious but half as potent as fentanyl
• very short acting so use CRI
• fast recovery
• bradycardia, hypotension, respiratory depression, histamine release
• non hepatic metabolism instead it is done in muscle and intestine
• very expensive

Question 8

Buprenorphine

Answer 8

• agonist-antagonist. partial mu agonist and kappa antagonist
• duration of 6-8 hours
• good oral absorption in cats
• may be difficult to reverse

Question 9

Tramadol

Answer 9

• weak mu agonist
• not a controlled substance so there is extra label use
• expensive
• OK for cats and horses
• only tend to dose 1-2 times per day
• not very effective in dogs
• serotonin and norepi reuptake inhibitor
• there is some a2 action (because it is close to mu receptor)
• good for acute and chronic pain that is moderate to severe
• often used in conjunction with NSAIDs for chronic pain and it may or may not cause sedation

Question 10

Meperidine

Answer 10

• primary activity at mu receptor
• good for acute pain and preanesthetic drug
• cheap
• metabolized to the active metabolite normeperidine
• increases heart rate
• some a2 agonist activity
• moderate length of action
• if given IV needs to be done slowly to avoid severe hypotension
• irritating if given SQ