Chlordiazepoxide — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	2-5 mg/kg (anxiety); 0.5-2 mg/kg (preanesthetic)	q8-12h	Duration: As needed; for anxiety, may be used short-term or as needed Notes: Titrate to effect; avoid long-term use due to tolerance and dependence.
Cat	PO	2-5 mg/kg (anxiety); 1-2 mg/kg (appetite stimulation)	q12-24h	Duration: As needed; short-term use recommended Notes: Cats may experience paradoxical excitement; use with caution.
Horse	IV	0.2-0.5 mg/kg	Once	Duration: Single dose for sedation Notes: Often used in combination with other sedatives; not approved in food animals.
Cattle	IV	0.5-1 mg/kg	Once	Duration: Single dose for sedation Notes: Extra-label use; withdrawal times must be observed.
Small Ruminants	IV	0.5-1 mg/kg	Once	Duration: Single dose for sedation Notes: Extra-label use; withdrawal times must be observed.
Rabbit	PO	1-2 mg/kg	q12-24h	Duration: Short-term Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications

Anxiety
Sedation
Muscle relaxation
Anticonvulsant (adjunctive)

Dog (Canine)

Anxiety disorders
Behavioral problems (e.g., noise phobia, separation anxiety)
Preanesthetic sedation
Muscle relaxation
Seizure control (adjunctive)

Cat (Feline)

Anxiety disorders
Behavioral problems (e.g., inappropriate urination, aggression)
Preanesthetic sedation
Appetite stimulation (historically)

Horse (Equine)

Anxiolysis
Sedation (in combination with other agents)
Muscle relaxation

Cattle (Bovine)

Sedation

Small Ruminants (Sheep / Goat)

Sedation

Rabbit & Small Mammals

Anxiolysis

Pharmacology & Mechanism of Action

Drug Class: Benzodiazepine | Pharmacological Group: Anxiolytic, Sedative-Hypnotic

Mechanism of Action: Chlordiazepoxide is a benzodiazepine that enhances the inhibitory effects of gamma-aminobutyric acid (GABA) at the GABA-A receptor. It binds to the benzodiazepine site on the receptor complex, increasing the frequency of chloride channel opening, leading to hyperpolarization of neurons and reduced neuronal excitability. This results in anxiolytic, sedative, muscle relaxant, and anticonvulsant effects.

Pharmacodynamics: Chlordiazepoxide produces dose-dependent central nervous system depression. At low doses, it has anxiolytic effects; at higher doses, it causes sedation, hypnosis, and muscle relaxation. It also has anticonvulsant properties. The drug does not have analgesic properties and may cause paradoxical excitement in some animals.

⚡ Pharmacokinetics Summary

Absorption: Chlordiazepoxide is well absorbed after oral administration. Peak plasma concentrations occur within 1-4 hours in most species. Food may delay absorption but not the extent.

Distribution: It is widely distributed throughout the body, crosses the blood-brain barrier and placenta, and is distributed into milk. It is highly lipophilic and accumulates in adipose tissue.

Metabolism: Chlordiazepoxide is extensively metabolized in the liver, primarily by oxidative pathways, to active metabolites including desmethylchlordiazepoxide, demoxepam, and nordazepam. These metabolites contribute to the pharmacological effects and have long half-lives.

Excretion: Metabolites are excreted primarily in the urine as glucuronide conjugates. A small amount is excreted in feces. The elimination half-life is prolonged in animals with hepatic or renal impairment.

Half-Life: Dogs: 5-10 hours (active metabolites longer); Cats: 5-10 hours; Horses: 2-4 hours; Humans: 24-48 hours (for reference)

Bioavailability: Oral bioavailability is high (approximately 80-100%) in most species, but may be reduced in some due to first-pass metabolism.

Protein Binding: Approximately 90-98% bound to plasma proteins.

Available Formulations & Strengths

Oral Capsule 5 mg, 10 mg, 25 mg (PO)

Oral Tablet 5 mg, 10 mg, 25 mg (PO)

Injectable Solution 100 mg/5 mL (20 mg/mL) (IM or IV)

Contraindications & Clinical Warnings

Contraindications:

Known hypersensitivity to benzodiazepines
Severe hepatic impairment
Acute narrow-angle glaucoma
Severe respiratory insufficiency
Concurrent use with other CNS depressants (relative contraindication)
Pregnancy (especially first trimester) unless benefits outweigh risks

Warnings & Clinical Precautions:

Use with caution in animals with renal or hepatic disease.
May cause paradoxical excitement, especially in cats and aggressive animals.
Long-term use may lead to tolerance and physical dependence; abrupt withdrawal may cause rebound anxiety or seizures.
Use with caution in debilitated or geriatric animals.
May cause muscle weakness and ataxia.
In food animals, extra-label use is prohibited in the US; withdrawal times must be established.
Avoid in animals with a history of aggression or unpredictable behavior.

Adverse Effects & Reactions

Common:

Sedation
Ataxia
Increased appetite
Paradoxical excitement (especially cats)
Muscle weakness

Serious / Severe:

Respiratory depression (with high doses or concurrent CNS depressants)
Hepatotoxicity (rare)
Blood dyscrasias (rare)
Dependence and withdrawal syndrome

Rare:

Hypotension
Gastrointestinal disturbances
Skin reactions
Bone marrow suppression

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other CNS depressants (barbiturates, opioids, phenothiazines)	Additive CNS depression and respiratory depression	High
Cimetidine	Decreased metabolism of chlordiazepoxide, increased plasma levels	Moderate
Ketoconazole	Inhibits CYP450 enzymes, increasing chlordiazepoxide levels	Moderate
Fluoxetine	May increase chlordiazepoxide levels via CYP inhibition	Moderate
Antacids	May decrease absorption of oral chlordiazepoxide	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Severe sedation
Ataxia
Coma
Respiratory depression
Hypotension
Hypothermia
Paradoxical excitation (rare)

Emergency Treatment Protocol: Treatment is primarily supportive. Induce vomiting if recent ingestion and animal is conscious. Administer activated charcoal. Provide respiratory support (oxygen, ventilation). Monitor vital signs. Flumazenil (benzodiazepine antagonist) may be used at 0.01-0.02 mg/kg IV, but use with caution as it may precipitate seizures in animals with underlying seizure disorders or in cases of mixed overdose.

Food Animal Withdrawal Times

Chlordiazepoxide is not approved for use in food animals in the US. Extra-label use is prohibited. In other countries, withdrawal times may be established; consult regulatory authorities.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature (20-25°C, excursions permitted to 15-30°C).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep in tightly closed container.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for human use; not FDA-approved for veterinary use, but may be used extra-label in companion animals.

Extra-Label (Off-Label) Use: In the US, extra-label use of chlordiazepoxide in food animals is prohibited by the FDA. In companion animals, extra-label use is permitted under AMDUCA with appropriate veterinary oversight.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Chlordiazepoxide is a benzodiazepine used in veterinary medicine primarily for its anxiolytic and sedative effects. It is most commonly used in dogs and cats for behavioral disorders such as anxiety and phobias. Due to its long half-life and active metabolites, it may be administered once or twice daily. However, its use has declined in favor of newer benzodiazepines (e.g., alprazolam) or other anxiolytics (e.g., SSRIs) due to concerns about tolerance and dependence. In horses, it is occasionally used for sedation, but other agents are preferred. In food animals, its use is restricted due to regulatory concerns. Always use with caution in animals with hepatic disease, and monitor for paradoxical excitement. Abrupt discontinuation after prolonged use should be avoided to prevent withdrawal symptoms.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)