8. Neuroleptics (major tranquilizers) Flashcards
(26 cards)
What are neuroleptics?
Neuroleptics are major tranquillizers, used for the treatment and management of symptoms associated with various psychiatric disorders
Drug groups under neuroleptics
1.Phenothiazines
2. Butyrphenones
Active substances for phenothiazines
- Acepromazine
- Chlorpromazine
- Propionylpromazine
Active substances for butyrphenones
- Azaperone
- Droperidol
- Fluanisone
Chemical structure of phenothiazine
Thiazine heterocyclic compound
Mechanism of action of phenothiazines
The phenothiazines have different mechanism:
Imagine a drug is like key and the receptors are like a lock, and when the key fits into the lock something will happen – When the drug binds to a receptor, something will happen
1. Dopaminergic receptor antagonist
2. Alpha-2 adrenoreceptor antagonistic
3. Muscarinic receptor interaction
4. H1 (Histamine) Receptor antagonism
5. 5-HT receptor antagonist
What does Dopaminergic receptor antagonist mean?
Dopamine is like a messenger protein, and when this is blocked, it can lead to tranquillizing effects (calming aggressive or anxious animals), an antiemetic effect. They can also cause CNS signs or movement disorders.
What does Alpha-2 adrenoreceptor antagonistic mean?
the alpha-2 adrenoreceptors are involved in regulating blood pressure and alertness.
By blocking these receptors, it can cause low blood pressure, which is a concern during surgery or in animals with heart conditions and during sedation
What does Muscarinic receptor interaction mean?
Muscarinic receptors are part of the parasympathetic nervous system, controlling functions like salivation, heart rate and digestion.
When a drug affects these receptors, it mainly causes side effects such as:
- Dry mouth
- Constipation
- Urinary retention
- Increased heart rate
What does H1 (Histamine) Receptor antagonism mean?
Histamine receptors are involved in allergic reactions and wakefulness.
Blocking these receptors can cause sedation, which can be useful for calming animals. It also has an antiseptic effect when blocked and is also used to treat allergic reactions.
What does 5-HT receptor antagonist mean?
5-HT receptors (serotonin receptors) are involved in mood and behavioural functions.
By blocking these receptors, it can influence the behaviour, reducing anxiety or affecting the appetite.
Pharmacological effect of phenothiazine
1. Sedation: Catalepsy-like immobilisation
2. Potentiation: Sedatives, hypnotics, analgesics
3. Vegetative tone decrease: increased relative sympathetic tone, circulation, central antiemetic effect, antihistamine activity, inhibition of regulation of body temperature
Pharmacokinetics of phenothiazine
Has a long withdrawal period
Administration: IV, IM, PO (buccal, rectal)
1. Absorption = Poor oral absorption, better in buccal and rectal use
2. Distribution = Good tissue distribution ⭢ crossing the BBB.
Slow onset of action.
Long duration
3. Metabolism = in liver
4. Excretion = via urine, in metabolites.
Slow elimination from the body
side effects of phenothiazine
- Hypotension; collapse, in horses excitation
- Tissue irritation
- Allergy
- Liver injury
- Hypothermia
- Penile prolapse in horses
- Third eyelid prolapse in dogs and cats
- Epilepsy
Indications of phenothiazine
- Calming and sedation of aggressive animals
- Premedication before general anaesthesia
Contraindications of phenothiazine
- Decreases motoric activity
- Not to use in dehydrated animals due to shock
- Not for epileptic or pseudpregnant animals
- Bulldogs and boxers might be oversensitive
- Not to be used before slaughter
Butyrphenone
More potent in treating acute symptoms. Also has some analgesic effect
Chemical strucutre of butyrphenone
Phenyl ring.
A ketone group
A butyl side chain
Mechanism of action for butyrphenones
- Dopamine inhibition (D2)
- NA (Noradrenaline) inhibition
- Anticholinergic effects on CNS
- With a weaker antagonistic effect on alpha-1 and H1 receptors
What does Dopamine inhibition (D2) mean?
The drug blocks or reduces the activity of dopamine, which is a neurotransmitter in the brain. Dopamine is involved in pleasure, motivation and movement
What does NA (Noradrenaline) inhibition mean?
The drug blocks or reduces the activity of noradrenaline, also called norepinephrine. Norepinephrine affects alertness, attention and the “fight-or-flight” response.
What does Anticholinergic effects on CNS mean?
The drug blocks or reduces the action of acetylcholine on the CNS.
Acetylcholine affects functions such as muscle control, memory and attention.
Blocking it can cause dry mouth, blurred vision, and confusion
What does With a weaker antagonistic effect on alpha-1 and H1 receptors mean?
Butyrphenones also block the alpha-1 and histamine receptors, but not as strongly.
Alpha-1 receptors are involved in blood pressure control, histamine receptors are involved in allergic reactions
Side effects of butyrphenone
- Transient salivation or panting
- Hypotension
- Respiratory stimulation
- Boar penile prolapse
