Phenothiazines Tranquilizers Antihistamines
Dose:
- IV: 0.01-0.04 mg/kg (0.05+ hits sedation plateau but increased CV effects), 15 min onset
- (Max 0.01 mg/kg for Boxer dogs)
- IM: 30 min onset
- PO: 30 min onset: unreliable absorption
- Dog: 1-3 mg/kg, F = 20%
- Horse: 0.1 - 0.4 mg/kg, F = 55%
- t1/2 = 3 - 7h, WP
- Safe drug = Large TI
Summary:
Minimal CV effect under 0.05 mg/kg (Hypotension)
Use in thermoregulated environment
Slight sedation
Anti emetic
No / minimal respiratory depression
No analgesia nor loss of consciousness if used alone
Pharmacokinetics:
Lipophilic drug (Cross BBB easily)
Intensive liver metabolism (Careful use with hepatopathy)
Excretion via urine
Effects:
- Antagonist of multiple receptors:
- Dopamine D2
- Histamine H
- Serotonin 5HT
- Alpha 1 α1
- Muscarinic Acetylcholine Receptor mAChr
Indication:
- Premedication
- Reduce Propofol in Fe from 7.2mg/kg to 5 mg/kg > Decreased respiratory depression
- Sedation (Tranquilizers and Behavior Modifiers)
- For travelling (With antiemetic effect)
- Neuroleptanalgesia = Superficial sleep
- ACP + Opioids (Butorphanol/Morphine/Buprenorphine/Fentanyl/Etorphine)
- Muscle relaxation + Analgesia
- BUT No loss of consciousness (Unlike less safe General anesthesia)
- Antiemetic (H and D2 antagonism) (Antiemetics)
- Decreased allergic reaction (H antagonism): 1st generation Antihistamines
Main side effects:
- α1 antagonist > vasodilation > hypotension
- Max 0.01 mg/kg for Boxer dogs
- Decreased Hematocrit (Anemia) (-20%)
- Prolonged penis prolapse: Dangerous for breeding Stallions
- Minimal CV effects under 0.05 mg/kg
- D2 and 5HT antagonism > Thermoregulation dysfunction / Hypothermia
- D2 antagonism:
- Extrapyramidal side effects (Parkinson’s-like: Seizures)
- Increased PRL (Maintains pseudopregnant state)
- In Behavior Modifiers treatment:
- Normal stress reaction is suppressed (Ataraxia)
- Paradoxical reaction: not for reactive dogs
Contraindications:
Hypovolemic / Dehydrated
Liver Failure / Porto Systemic Shunt PSS
Breeding stallions
Pseudopregnant animals
Boxer dogs
Non thermoregulated environment
Combined use with other Dopamine Antagonists (Metoclopramide)