Clonazepam — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	0.1-0.5 mg/kg	q8-12h	Duration: Variable; for seizures, long-term as needed Notes: Start at low end and titrate to effect. May cause sedation initially.
Cat	PO	0.05-0.2 mg/kg	q12h	Duration: Variable; for seizures or anxiety Notes: Use cautiously in cats with hepatic disease.
Horse	PO	0.02-0.05 mg/kg	q12h	Duration: Short-term for anxiety or seizures Notes: Limited data; use with caution.
Rabbit	PO	0.1-0.5 mg/kg	q12h	Duration: Variable Notes: Off-label use; monitor for sedation.

Clinical Indications & Species Uses

General Indications

Adjunctive therapy for seizures
Anxiety and panic disorders
Muscle spasms
Behavioral disorders (e.g., phobias)

Dog (Canine)

Adjunctive therapy for seizures (especially myoclonic and photic-induced seizures)
Anxiety disorders (as an alternative to diazepam)
Status epilepticus (when IV diazepam is unavailable, oral clonazepam may be used as a temporary measure)

Cat (Feline)

Seizure control (adjunctive)
Anxiety-related behavioral disorders (e.g., inappropriate urination, aggression)

Horse (Equine)

Anxiolytic in handling situations (off-label)

Pharmacology & Mechanism of Action

Drug Class: Benzodiazepine | Pharmacological Group: Anticonvulsant, Anxiolytic, Muscle Relaxant

Mechanism of Action: Clonazepam 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 anticonvulsant, anxiolytic, sedative, and muscle relaxant effects.

Pharmacodynamics: Clonazepam suppresses the spread of seizure activity in the brain by enhancing GABAergic inhibition. It also has effects on the limbic system and motor cortex, contributing to its anxiolytic and anticonvulsant properties. In veterinary patients, it is primarily used for its anticonvulsant effects, though it may also be used for behavioral disorders.

⚡ Pharmacokinetics Summary

Absorption: Clonazepam is well absorbed after oral administration, with peak plasma concentrations occurring within 1-4 hours in most species. Bioavailability is high (approximately 90% in humans, likely similar in animals).

Distribution: Clonazepam is highly lipid-soluble and distributes widely throughout the body, including the central nervous system. It crosses the blood-brain barrier and placenta, and is secreted into milk. Protein binding is approximately 85% in humans, but may vary in animals.

Metabolism: Clonazepam is extensively metabolized in the liver, primarily by cytochrome P450 enzymes (CYP3A4) to inactive metabolites, including 7-aminoclonazepam and 7-acetamidoclonazepam. These metabolites are then conjugated and excreted.

Excretion: Metabolites are excreted primarily in the urine (up to 70%) and feces (up to 30%). A small fraction of the drug is excreted unchanged. The elimination half-life is species-dependent.

Half-Life: Dogs: 1-2 hours (short); Cats: 2-4 hours; Horses: 1-2 hours; Humans: 20-40 hours (for reference).

Bioavailability: Oral bioavailability is high, approximately 90% in humans; likely similar in animals.

Protein Binding: Approximately 85% in humans; may vary in animals.

Available Formulations & Strengths

Oral Tablet 0.5 mg, 1 mg, 2 mg (PO)

Oral Disintegrating Tablet 0.125 mg, 0.25 mg, 0.5 mg, 1 mg, 2 mg (PO)

Injectable Solution (not commonly used in veterinary medicine) 1 mg/mL (for IV use in humans) (IV)

Contraindications & Clinical Warnings

Contraindications:

Known hypersensitivity to benzodiazepines
Severe hepatic insufficiency
Acute narrow-angle glaucoma
Severe respiratory insufficiency
Myasthenia gravis
Concurrent use with other CNS depressants (relative contraindication)

Warnings & Clinical Precautions:

Use with caution in patients with hepatic or renal disease.
May cause paradoxical excitation (especially in cats and some dogs).
Tolerance and dependence can develop with prolonged use; abrupt withdrawal may cause rebound seizures or anxiety.
Use with caution in pregnant or lactating animals; safety not established.
May cause sedation and ataxia; monitor when used in working animals.
In food animals, extra-label use is prohibited; not approved for use in food-producing animals.

Adverse Effects & Reactions

Common:

Sedation
Ataxia
Increased appetite
Paradoxical excitation (especially in cats)
Hypersalivation

Serious / Severe:

Respiratory depression
Hepatic toxicity (rare)
Blood dyscrasias (rare)
Paradoxical aggression

Rare:

Hypotension
Urinary retention
Skin rash
Jaundice

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other CNS depressants (e.g., barbiturates, opioids, phenothiazines)	Additive sedation and respiratory depression	High
Cimetidine	May increase clonazepam plasma levels by inhibiting metabolism	Moderate
Phenobarbital	May decrease clonazepam levels due to enzyme induction; also additive CNS depression	Moderate
Fluoxetine	May increase clonazepam levels via CYP inhibition	Moderate
Ketoconazole	May increase clonazepam levels via CYP3A4 inhibition	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

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

Emergency Treatment Protocol: Treatment is primarily supportive. Induce vomiting if recent ingestion and patient is conscious. Administer activated charcoal to reduce absorption. Provide respiratory support if needed. Flumazenil (benzodiazepine antagonist) can be used in severe cases, but use with caution as it may precipitate seizures in patients on chronic benzodiazepine therapy.

Food Animal Withdrawal Times

Not approved for use in food-producing animals. Extra-label use is prohibited in food animals in the US.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (20-25°C, 68-77°F).

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

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; used off-label in animals.

Extra-Label (Off-Label) Use: In the US, extra-label use in animals is permitted under AMDUCA for non-food animals, but prohibited in food-producing animals. In the EU, similar restrictions apply.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Clonazepam is a benzodiazepine used primarily as an adjunctive anticonvulsant in dogs and cats, particularly for myoclonic seizures and certain behavioral disorders. It has a rapid onset of action and is well absorbed orally. However, its short half-life in dogs and cats may require frequent dosing. Tolerance can develop, and abrupt discontinuation should be avoided to prevent withdrawal seizures. It is a controlled substance (Schedule IV) and should be handled accordingly. In veterinary practice, it is often used when diazepam is ineffective or not tolerated. Monitoring for sedation and hepatic function is recommended during long-term therapy.

References & Literature

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