Veterinary Neuropharmacology

PHENOTHIAZINES

Phenothiazines: Chlorpromazine, Acepromazine, Promethazine, Triflupromazine.

Mainly used as a tranquilizers (ataratics or neuroleptics) that relieve anxiety without undue sedation facilitating quietening and handling of animals.

• Wide range of central and peripheral effects – act on dopamine, norepinephrine, 5HT and histamine receptors.
• Decrease spontaneous motor activity
• Depress the brain stem and connections to the cortex
• At high doses catalepsy is produced – animals remain immobile at a fixed position for a long time
• Powerful antiemetic action
• Antiadrenergic action on heart result in Cardiovascular collapse
• Chlorpromazine –(Largactil) – prototype drug which was popular in human and veterinary medicine. 
• Widely used in humans for antipsychosis
• Acepromazine – popular drug
• Good sedative – lasts 4 – 6 h but much high reported in dogs
• May show initial excitement
• Also cause hypothermia and antiemetic effect
• Causes paralysis of the retractor penis resulting in  priapism and paralysis of the penis in stallion and bulls and affect their market value
• Also causes prolapse of third eyelid
• Used as antispasmodic in colic in horses
• Used as a sedative premedication
• Also in pets for antiemesis
• Promethazine – used as an antihistaminic
• Triflupromazine (Siquil) as a sedative, as a restraint and as a preanaesthetic
• Methotripromazine – agent with significant analgesic action