Topic 8 - Neuroleptics (major tranquilizers) Flashcards
(23 cards)
What are neuroleptic drugs?
Known as antipsychotic medications, are medications that block dopamine receptors in the nervous system
Major groups of neuroleptic drugs
Phenothiazines
Butyophenones
Definition of phenothiazines
Used as tranquilizers, preanesthetic, antiemetic and as treatment fro CNS agitation after specific drug overdoses
Definition of butyophenones
It is more potent than phenothiazines. It has some analgesic (painkiller) effect
Active substances of phenothiazines
Acepromazine
Chlorpromazine
Propionylpromazine
Prometazine
Active substances of butyophenones
Azaperone (SU)
Dropeidol
Flunanisone
Haloperidol
Phenothiazine, mechanism of action:
- Dopaminergic receptor, antagonistic
- Alpha-adrenoreceptor antagonistic
- Muscarinic receptor
- Histamine receptor antagonistic
- Serotonin receptor antagonistic
Which effect does the dopaminergic receptor antagonistic have?
Antipsychotic effect, Antiemetic effect, Prolactin
increase, Parkinson-syndrome
Which effect does the Alpha-adrenoreceptor antagonistic have?
Hypotension, Sedation
Which effect does the Muscarinic receptor antagonistic have?
Mainly side effects
Which effect does the Histamine receptor antagonistic have?
Sedation, Antiemetic effect
Which effect does the Serotonin receptor antagonistic have?
Enhancement of several effects
Pharmacological effect of phenothiazone
Sedation (catalepsy like immobilization),
Potentiation (sedatives, hypnotics, analgesics),
Vegetative tone decrease, with increased relative
sympathetic tone, circulation, central antiemetic
effect, antihistamine activity, inhibition of
regulation of body temperature
Pharmacokinetical properties of phenothiazine
Absorption: Poor oral absorption (F=0.2): better in buccal, rectal use
Distribution: Good tissue distribution: cross BBB. Slow onset of activity (after IV use too), Long duration
of activity (>10-12 h) larger dose increase, plasma protein binding approx 95%
Metabolism: metabolism in liver
Excretion: excretion via urine, in metabolites, Slow
elimination from the body (Equidae 122/2013 EC
reg).
Long withdrawal period (Cascade)
Side effects of phenothiazine
1.TI (therapeutic index) relative big
2. Hypotension: collapse, in horses excitation
3.Tissue irritation, allergy, liver injury, hypothermia,
Penile Prolapse in horses and third eyelid (nictating membrane) prolapse in pets (cats, dogs), Prolactin increase, FSH, LH and oxytocin decrease. Epilepsy, extrapyrimidal symptoms (higher dose, tremors, shivering, ridgidity)
Indications for phenothiazine
'’1.** Calming, sedation of aggressive animals, eg. To
alleviate handling during veterinary investigations
and transport (without hypnotic effect: catalepsy like)
2. Premedication before general anaesthesia and
neuroleptanalgesia
Contraindications for phenothiazines
1. May cause paradoxical reactions and phobias can get worse
2. Decreased motoric activity (without analgesia)
3. Not for dehydrated animals or in case of shock
4. Not for epileptic and pseudopregnant animals
5. Bulldogs and Boxers may be oversensitive: idiosyncracy, MDR 1 Gene Breeds (+/+)
6. Do NOT use before transportation to Abattoir
(slaughterhouse)
Administration of phenothiazines
IV
IM
PO
(Buccal, rectal)
Dosages for phenothiazones
Dosages in a large range (interspecies differences)
0.05 - 5 mg/kg
Butyrophenones, mechanism of action
1. Dopamine Inhibition (D2)
2. NA (Noradrenaline) inhibition
3. Anticholinergic effects in CNS
4. With weaker antagonistic effect on alpha1 and H1 (histamine) receptors
Butyrphenones, pharmacological effect
More potent than phenothiazines, some analgesic effect
Side effects of butyphenones
Transient salivation or panting
Hypotension, respiratory stimulation, Boar penile
prolapse
Contraindications for butyrphenones
Avoid use in very cold condition (but can reduce hyper thermia caused by Halothane)
