Sedatives Flashcards
tranquilizers induce __________, whereas sedatives induce _____________
calmness; sleepiness
what are the 3 main types of chemical restraint agents
1) tranquilizers/sedatives
2) anesthetics
3) opiods
what are the 3 types of sedatives
1) phenothiazines
2) alpha-2 agonists
3) benziodiazepines
what is a huge caution regarding many IV CNS depressants
accidental injection into the carotid artery (instead of the jugular vein) can be fatal -> immediate convulsive seizures and death
sedated patients require (higher/lower) doses of induction agents, often on the order of ______ the dose required to induce an un-premedicated patient, and also often require (higher/lower) doses of inhalant anesthetic
lower; half; lower
T/F sedatives allow a smoother recovery from general anesthetics, but only if the procedure performed was painful
F; will smooth recovery regardless of pain as recovery from general anesthesia can be rough
what is the major phenothiazine sedative used
acepromazine
acepromazine is the phenothiazine of choice for all species except:
pigs
what are 4 effects of acepromazine
1) reduces fear and anxiety
2) reduces responses to stimuli
3) induces lethargy
4) relaxes muscles
onset of sedatives is fastest in what kind of environment
quiet (ex. cage rest for 15 min)
what is the main use of acepromazine
restraint (ex. pre-op)
what is the time to clinical effect for acepromazine for the following routes:
1) IV
2) IM
3) Oral
1) 15 min
2) 30 min
3) 60 min
what is the mechanism of action of acepromazine
Main action: blocks D2 (dopamine) receptors in the brain -> dopamine needed for wakefulness and motor activity -> sedation, reduced anxiety
Note: also blocks peripheral α1 receptors
what are the side effects of acepromazine (and other phenothiazines) and how does this happen
hypotension and sphincter relaxation; due to α1 receptor antagonism on the blood vessels and sphincters
T/F acepromazine can cause hyperthermia, regurgitation in all species and excessive vagal tone in all breeds but brachycephalic breeds
F:
- causes hypothermia
- regurgitation in ruminants
- excessive vagal tone uncommon except for in brachycephalic breeds
what is a concern regarding acepromazine and male horses
retractor penis muscles are adrenergic, so acepromazine causes penile prolapse -> can last long enough for edema to occur -> constriction of blood supply -> ischemic necrosis
what are some contraindications for acepromazine (phenothiazine) use
1) hypovolemic/shocky patients
2) breeding stallions
3) organophosphate poisoning
4) boxers
5) herding breeds with specific mutations (p-gp and MDR1)
T/F acepromazine should not be given to epileptic patients because it can promote seizures
FALSE
what is used in place of acepromazine for pigs and why
azaperone; has a 1 day withdrawal time (vs 7 days)
T/F azaperone can be used to stop fighting in pigs
F; just prolongs the fighting
what are the 4 alpha-2 agonists we discuss; which is the least potent
1) xylazine
2) detomidine
3) dexmetetomidine
4) romifidine
xylazine is the least potent
what is unique about xylazine compared to other alpha-2 agonists
the analgesic effect lasts only approx 30 min
how long does xylazine sedation last
2h (dose-dependent)
what is the mechanism of action of xylazine and what are the 5 main effects
α2 agonist -> opens K channels -> inhibit NT release in brain pathways for:
- wakefulness (sedation)
- pain (analgesia)
- BP control (hypotension)
- motor activity (muscle relaxation)
- respiration (drop in O2)
what animals are most prone to respiratory side-effects of xylazine and why
small ruminants, calves, sick cattle; via degranulation of pulmonary intravascular macrophages in ruminants
what is a transient side effect of alpha-2 agonists, such as xylazine and how is it mediated
transient vasoconstriction and increased bp - via stimulation of peripheral alpha 1 and alpha 2b receptors on blood vessels
what is a potential adverse effect of xylazine in large animals; why not in small animals?
hypotension (due to transient hypertension from alpha 1/2b receptors) followed by bradycardia (due to alpha 2a receptors); small animals tend to have normal or high bp
what is a side effect of xylazine in cats that can be used clinically
induces vomiting in 2-5 min
the effects of xylazine can be reversed by what drugs
alpha 2 antagonists:
- atipamezole
- yohimbine
what species is highly sensitive to alpha-2 agonists and why; what dose do we give them
domestic ruminants; possess an alpha-2D receptor other species lack; get 1/10th regular dose
how would you use xylazine in large animals in the following cases:
- for restraint
- for general anesthesia
- for a short surgical procedure
- alone
- with ketamine
- with opioid
detomidine is approved for what species
horses only
if a horse is still kicking when given detomidine, what can you do
can give guaifenesin if animal is light, or add an opioid
when would you choose detomidine over a xylazine for treating horses
if pain is greater (as analgesic effects last as long as sedative effects) or if a longer effect is desired
peak detomidine sedation occurs in
5-20 min
dexmetetomidine is used in what species
dogs and cats
peak dexmetetomidine sedation occurs in
20-30 min
T/F dexmetetomidine worsens the respiratory depression caused by opioids
T
romifidine:
- approved for what species
- main benefit compared to other sedatives
- horses
- less head droop and ataxia
what is a controversy of romifidine
analgesic effect is questionable
what are the reversal agents for alpha-2 agonists
atipamezole, yohimbine
how is atipamezole or yohimbine given and why
intramuscularly; giving IV can be fatal
T/F atipamezole is more specific to α1 than α2
F; other way around
what is the main benzodiazepine
diazepam
what are the 3 effects of diazepam
- muscle relaxant
- sedative
- anticonvulsant
how does diazepam/ other benzodiazepines work
inhibits APs by stimulating the activity of GABA
T/F benzodiazepines can be safely used with other CNS depressants
F; VERY BAD, DO NOT DO
T/F when used alone benzodiazepines have little effect on the cardiovascular system
T
you accidentally overdose a patient on diazepam (oops!) - what do you give them to reverse the effects
flumazenil
benzodiazepines cause dose-dependent ______________ depression
respiratory
what happens if you give a cat benzodiazepines chronically
they get an idiosyncratic Type B ADR that causes fulminant (aka severe and sudden) hepatic necrosis
what is a clinical use of benzodiazepines in cats
appetite stimulation
what is a potential behavioural problem observed when giving dogs and horses benzodiazepines
aggression and excitement
what is a common induction mixture in small animal medicine involving benzodiazepines
1:1 ketamine: diazepam
if you want a rapidly effective benzodiazepine, what do you choose and why
midazolam over diazepam; water soluble so better for IM use
what is a benefit of guaifenesin over alpha-2 agonists and opioids
little to no cardiovascular or respiratory depression
what type of drug is added to IV and crystallizes at room temperature, making it look like a bag full of styrofoam
guaifenesin
