Colchicine — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	0.03-0.06 mg/kg	q12-24h	Duration: Long-term (months to years) for chronic conditions Notes: Start at low dose and titrate up. Monitor for gastrointestinal side effects.
Cat	PO	0.03-0.05 mg/kg	q24h	Duration: Long-term for chronic conditions Notes: Cats are more sensitive to colchicine; use with caution.
Horse	PO	0.01-0.02 mg/kg	q12-24h	Duration: Variable, often long-term for uveitis Notes: Use with caution; monitor for diarrhea.
Cattle	PO	0.02-0.05 mg/kg	q24h	Duration: Short-term for experimental use Notes: Not approved; extra-label use only.
Small Ruminants	PO	0.02-0.05 mg/kg	q24h	Duration: Short-term for experimental use Notes: Not approved; extra-label use only.
Rabbit	PO	0.03-0.05 mg/kg	q24h	Duration: Variable Notes: Limited data; use with caution.
Bird/Poultry	PO	0.02-0.05 mg/kg	q24h	Duration: Variable Notes: Limited data; use with caution.
Exotic/Other	PO	0.02-0.05 mg/kg	q24h	Duration: Variable Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications

Treatment of inflammatory conditions, amyloidosis, and fibrotic diseases

Dog (Canine)

Treatment of familial Shar-Pei fever
Amyloidosis (especially in Chinese Shar-Peis)
Chronic hepatitis with fibrosis
Immune-mediated diseases (adjunctive therapy)
Idiopathic pulmonary fibrosis (off-label)

Cat (Feline)

Feline infectious peritonitis (FIP) – experimental
Amyloidosis (rare)
Chronic inflammatory conditions (off-label)

Horse (Equine)

Recurrent uveitis (equine recurrent uveitis) – adjunctive
Chronic laminitis (experimental)
Inflammatory conditions (off-label)

Cattle (Bovine)

Experimental for inflammatory conditions

Small Ruminants (Sheep / Goat)

Experimental for inflammatory conditions

Rabbit & Small Mammals

Experimental for hepatic fibrosis

Avian & Poultry

Experimental for amyloidosis

Exotic & Other Species

Experimental for inflammatory conditions in reptiles and small mammals

Pharmacology & Mechanism of Action

Drug Class: Anti-inflammatory agent | Pharmacological Group: Alkaloid, microtubule inhibitor

Mechanism of Action: Colchicine binds to tubulin, inhibiting microtubule polymerization and thus disrupting mitotic spindle formation, cell motility, and intracellular transport. It also interferes with leukocyte chemotaxis, phagocytosis, and lysosomal degranulation, reducing the inflammatory response. Additionally, it inhibits the release of inflammatory cytokines and reduces the deposition of amyloid fibrils.

Pharmacodynamics: Colchicine exerts its anti-inflammatory effects primarily by suppressing neutrophil activity and reducing the inflammatory response to monosodium urate crystals and other inflammatory stimuli. It also has antifibrotic effects and can reduce collagen deposition. In veterinary medicine, it is used to treat inflammatory and fibrotic conditions, particularly in the liver and joints.

⚡ Pharmacokinetics Summary

Absorption: Rapidly absorbed from the gastrointestinal tract after oral administration. Peak plasma concentrations occur within 1-2 hours in most species.

Distribution: Widely distributed throughout the body, with high concentrations in the liver, spleen, kidneys, and intestinal mucosa. It crosses the placenta and is excreted in milk.

Metabolism: Metabolized primarily in the liver via deacetylation and demethylation. Some metabolism occurs in the intestinal wall.

Excretion: Excreted primarily in bile and feces, with about 10-20% excreted unchanged in the urine. Enterohepatic recirculation occurs.

Half-Life: Dogs: approximately 4-6 hours; Cats: approximately 2-4 hours; Horses: approximately 1-2 hours; Cattle: approximately 2-3 hours.

Bioavailability: Oral bioavailability is approximately 40-50% in dogs and cats, with significant first-pass metabolism.

Protein Binding: Approximately 30-50% bound to plasma proteins.

Available Formulations & Strengths

Oral Tablet 0.6 mg (PO)

Oral Tablet 0.5 mg (PO)

Oral Solution 0.6 mg/5 mL (PO)

Injectable Solution 0.5 mg/mL (IV)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to colchicine
Severe renal or hepatic impairment
Pregnancy (especially in animals with known teratogenic risk)
Lactating animals (unless benefit outweighs risk)
Concurrent use with P-glycoprotein inhibitors (e.g., cyclosporine, ketoconazole) due to increased toxicity risk

Warnings & Clinical Precautions:

Use with caution in animals with gastrointestinal disease, as colchicine can cause severe diarrhea.
Monitor complete blood count and liver enzymes during long-term therapy.
Dose reduction may be necessary in animals with renal or hepatic insufficiency.
Avoid in animals with bone marrow suppression.
Use with caution in young animals due to potential effects on growth.
In food animals, observe withdrawal times; extra-label use is prohibited in some countries.

Adverse Effects & Reactions

Common:

Gastrointestinal upset (vomiting, diarrhea, anorexia)
Salivation
Lethargy

Serious / Severe:

Bone marrow suppression (leukopenia, thrombocytopenia)
Hepatotoxicity
Nephrotoxicity
Peripheral neuropathy
Myopathy

Rare:

Alopecia
Teratogenic effects
Bone marrow aplasia
Seizures

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Cyclosporine	Increased risk of colchicine toxicity due to P-glycoprotein inhibition.	High
Ketoconazole	Increased plasma levels of colchicine, leading to toxicity.	High
Macrolide antibiotics (e.g., erythromycin, clarithromycin)	Increased colchicine levels and risk of toxicity.	High
Statins (e.g., atorvastatin)	Increased risk of myopathy and rhabdomyolysis.	Moderate
NSAIDs	Additive gastrointestinal irritation and potential renal effects.	Moderate
Digoxin	Possible increased digoxin levels due to P-glycoprotein interaction.	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Severe vomiting and diarrhea (often bloody)
Abdominal pain
Bone marrow suppression
Hepatic and renal failure
Cardiovascular collapse
Respiratory depression
Seizures

Emergency Treatment Protocol: Immediate decontamination (induction of vomiting if recent ingestion, gastric lavage, activated charcoal). Provide supportive care: IV fluids, electrolyte replacement, monitoring of vital signs. Treat bone marrow suppression with colony-stimulating factors if severe. There is no specific antidote. In severe cases, consider hemodialysis or hemoperfusion.

Food Animal Withdrawal Times

🥩 Meat: 28 days🥛 Milk: 7 days

Colchicine is not approved for use in food animals in many countries. Withdrawal times are extrapolated from human data and may not be reliable. Extra-label use in food animals is prohibited in some regions. Consult regulatory authorities.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (20-25°C) in a tight, light-resistant container.

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

Handling & Special Conditions: Protect from moisture and light. Keep out of reach of children and animals.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use in the US. It is a human drug used extra-label in animals.

Extra-Label (Off-Label) Use: In the US, extra-label use of colchicine in animals is permitted under AMDUCA for non-food animals. For food animals, extra-label use is prohibited if an approved animal drug exists that is labeled for the condition. Colchicine is not approved for veterinary use in food animals; therefore, its use in food animals is not allowed.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Colchicine is a potent anti-inflammatory agent used primarily in dogs for familial Shar-Pei fever and amyloidosis. It is also used off-label for various fibrotic and inflammatory conditions. Due to its narrow therapeutic index, careful dosing and monitoring are essential. Gastrointestinal side effects are common and may limit use. In cats, it is rarely used due to increased sensitivity. In horses, it may be used for recurrent uveitis, but its efficacy is variable. Always consider potential drug interactions, especially with P-glycoprotein inhibitors. For food animals, avoid use due to lack of withdrawal data and regulatory restrictions.

References & Literature

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