Sedatives Flashcards
Human terms Sedative Low dose High dose Vet terms
Low - clam and drowsy. Not v responsive to external stimuli but can be roused
High - Unconscious, not anaesthesia but will fall asleep. Can still be roused. e.g. too much wine
Vet terms - drugs that are most similar to human sedatives but some species no matter how much you give, won’t fall asleep.
Tranquiliser
Low dose
High dose
Low - calm but alert adn responsive. Can respond to external stimuli, just not that bothered about them
High - altered state of consciousness = catalepsy. not sleep or anaesthesia and can be hyper!.
Anxiolytic
“Loss of anxiety”
Calm with altered response to stimuli. So normal stress situations animal doesn’t react. No fight or flight. Reduced cortisol. Behaviourists dislike this term.
Neuroleptic
relates specifically to the effects of phenothiazines or butyrophenones in the CNS
Neuroleptanalgesia
relates to the combination of a neuroleptic and an opioid, e.g. the phenothiazine acepromazine (ACP) and buprenorphine, OR fluanisone and fentanyl (Hypnorm)
What are the 4 classes of sedatives?
- Alpha-2 agonists
- Phenothiazines
- Butyrophenones
- Benzodiazepines
Alpha-2 agonists MOA general
- Most common sedative sued - important to know this MOA!
- NT noradrenaline
- 2 opposite outcomes depending on periphery or CNS
- Receptors post synaptic (periphery)= sympathomimesis, e.g. vasoconstriction
Receptors (CNS) pre synaptic = Sympatholysis = sedation
Alpha-2 agonists MOA periphery
- Noradrenaline NT released from pre synaptic neurone
- across cleft
- Binds to alpha 2 receptor on effector organ/ posty synaptic neurone
- causes Sympathomimesis
- result = continuation of sympathetic stimulation/ sympathomimesis
Alpha-2 agonists MOA CNS
- Can have pre synaptic alpha 2 receptors
- so NT released from pre and binds to pre
- Caused negative feedback and stops any further noradrenaline release
- result = sympatholysis = sedation
Route of administration of alpha 2 agonist
- Injectable preparations - water soluble so either IV or IM
- molecules themselves are lipid soluble so can be injected subcutaneously or epidurally
- Can also cross across mucosal including skin = can be admin orally. No swallow, just stay in mouth (gel under tongue)
- Can cross YOUR mucosal lining!!!!! WEAR GLOVES
Main effects alpha 2 agonists
- sedation
- Analgesia (lasts about 1/3rd length of sedation)
- muscle relaxation
- o An ‘anaesthetic sparing’ agent - can reduce dose of propofol by 50%
Side effects alpha 2 adrenoreceptor agonists
- Deleterious CV effects:
o CV suppression: vasoconstriction causes increased afterload on the heart, vagally mediated reflex bradycardia due to increased PNS tone, central sympatholysis results in PNS dominance = persistent bradycardia+ vasodilation - Diuresis (collection of urine as suppress release and action ADH),
- Sweating, particularly horses
- hyperglycaemia (reduce insulin secretion), muscle relaxation issue for brachycephalic breeds
What about alpha 2 agonists and antagonising them?
- Can antagonise the agonist!
• Licensed for cats and dogs Antagonist = atipamezole - means you can achieve significant clinical effects (sedation) and then once need for those effects has passed you can antagonise the agonist and not have to wait for the effects to wear off
- o But you antagonise alpha 2s, antagonise ALL effects e.g. analgesia = if done something painful not great
o AND over dosage of antagonist leads to opposite effects = excitement and hyperalgesia. BE CAREFUL WHEN USE ANTAGONISTS!
Name the licensed short acting drug for small animals
Xylazine
Same for cattle and hroses!
Name the licensed long acting drug for small animals
medetomidine
dexmedetomidine
