2- Types of premeds Flashcards
List the 6 drug groups of pre-medications
Opioids
Alpha-2 agonist
Phenothiazines
Benzodiazepine
NMDA Receptor antagonists
Anticholinergics
Give 3 examples of an opiod
Methadone
Fentanyl
Pethidine
Buprenorphine
Butorphanol
(Morphine - but not licensed)
Why is an opioid included in a pre-med?
Provide sedation & analgesia
What are the 4 receptors opioids act at?
MU
Kappa
Delta
Nociception
What receptors does butorphanol act at and What is its limitation?
MU antagonist & Kappa agonist
Provides good sedation but is has poor and short-lived analgesia
Would be ideal for non-painful procedures
T/F Methadone and Fentanyl are Full MU agonsits
True
Which types of opioids have the most analgesic effects
Full Mu agonists
methadone, fentanyl, pethidine and morphine
What effect does an opioid have on the GI system?
Reduce motility & decreases gastric emptying
What effects do opioids have on cardiovascular system
cause minimal cardiovascular depression and are often used in very sick patients
What drug antagonises opioids?
Naloxone
Give 2 examples of an alpha-2 agonist
Medetomidine
Dexmedetomidine
Xylazine
Detomidine
Romifidine
Which alpha-2 agonists are most commonly used in small animal practice
Medetomidine and dexmedetomidine
Why is xylazine less commonly used in small animals?
Poor affinity for alpha 2- receptors thus more side effects
What is the aim of an alpha-2 agonist?
Profound dose dependant sedation & good analgesia (short-lived)
What is detomidine licensed for
is licenced in horses and cattle
What effect do alpha-2 agonists have on the liver?
reduced blood flow to the liver & hepatic metabolism , shouldn’t use it in liver disease patients
Alpha 2 agonists have significant effects on what system?
Cardiovascular
Why wouldn’t you use an alpha 2 agonist in a unstable diabetic patient?
Reduces endogenous insulin secretion = causes transient hyperglycaemia
What drug do you use to antagonise an alpha-2 agonist?
Atipamezole
What effect does alpha-2 agonist have on MAC
They have marked drug sparing effects
they reduce MAC and therefore the amount of inhalation agent required and the amount of induction agent.
What can alpha-2 agonist do in cats
They can cause emesis, particularly in cats if used alone
What is the only licensed phenothiazine? & what is its aim?
Acepromazine (ACP) - contributes to sedation & provides anxiolytics
NO ANALGESIC PROPERTIES
What receptors do phenothiazines work out?
Centrally acting by antagonising D1/D2 receptor
Also act on alpha-1 muscarinic & H1 receptors
What role does alpha-1 antagonism have on blood vessels? & why is this a problem with phenothiazines
Vasodilation
Antagonise alpha 1 receptors = use causes vasodilation causing hypotension & hypothermia
Also can’t antagonise this drug which means this effect can be difficult to manage
How long does it take for phenothiazines to take effect
relatively slow to effect taking about 30-40 minutes when administered by IM injection and lasts about 6-8 hours in healthy animals
Define Neuroleptanalgesia
is the combination of an opioid and a tranquilizer or sedative and reduces the amount of each required and results in improved sedation.
So this is what you’d get if you combined an opioid and acepromazine.
List the 2 Benzodiazepines and what animals they are licensed in
Midazolam (horses) & Diazepam (Dogs/cats)
What receptor do benzo’s work at?
GABA-A receptor
What is the aim of benzos?
Anxiolysis, sedation & hypnosis
(Not an analgesic)
The degree of sedation is poor - not something you’d give to healthy patient.
Good for sicker patients as minimal resp and cardio depression
Benzos are also used for..
seizing patients as they are anti-convulsants
What is the antagonist called for benzodiazepines?
Flumazenil
What drug class is Ketamine under?
NMDA receptor antagonists
At high doses ketamine is a …
Dissociative anaesthetic
At low doses ketamine results in…
Sedation
When ketamine is used alone it is a poor…..thus we combine it with….
Muscle relaxant = Miadazolam(benzo) or alpha 2
How long does ketamine tend to last
It’s relatively short acting (30-45 minutes)
What effects do anticholinergics have?
Reduce bradycardia, respiratory tract secretions
Name some examples of anticholinergics
Atropine, Glycopyrrolate
What are the side effects of anticholinergics in the premed
mydriasis, reduced gut motility, bronchodilation etc.
so not routinely used in premed
What Is alfaxalone?
Neuroactive steroid
What type of receptors do birds have a high proportion of
kappa receptors
means that butorphanol which is a MU agonist and kappa agonist could be a good choice for pre-med in birds
Which animals should alpha-2 agonists not be used in
need to be careful in blocked animals
sick animals due to cardio effects
unstable diabetics
