Latanoprost — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	Topical ophthalmic	1 drop (0.005% solution) per eye	q24h (once daily)	Duration: Chronic, as needed Notes: Administer in the evening to maximize nocturnal IOP reduction. May be combined with other glaucoma medications.
Cat	Topical ophthalmic	1 drop (0.005% solution) per eye	q24h (once daily)	Duration: Chronic, as needed Notes: Monitor for local irritation. Use with caution in cats with uveitis.
Horse	Topical ophthalmic	1 drop (0.005% solution) per eye	q12-24h (once or twice daily)	Duration: Chronic, as needed Notes: May cause transient miosis and increased aqueous flare. Use in conjunction with anti-inflammatory therapy for uveitis.
Rabbit	Topical ophthalmic	1 drop (0.005% solution) per eye	q24h	Duration: As needed Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications

Treatment of ocular hypertension and glaucoma in veterinary patients

Dog (Canine)

Reduction of elevated intraocular pressure in glaucoma
Maintenance therapy for primary glaucoma
Adjunct to other glaucoma medications

Cat (Feline)

Reduction of elevated intraocular pressure in glaucoma
Management of primary and secondary glaucoma

Horse (Equine)

Reduction of intraocular pressure in equine recurrent uveitis-associated glaucoma
Adjunct in uveitis therapy

Rabbit & Small Mammals

Reduction of intraocular pressure in experimental glaucoma models
May be used off-label for glaucoma

Exotic & Other Species

May be used in some exotic species for glaucoma, but limited data

Pharmacology & Mechanism of Action

Drug Class: Prostaglandin F2α analogue | Pharmacological Group: Ophthalmic hypotensive agent

Mechanism of Action: Latanoprost is a selective prostaglandin F2α receptor agonist that increases the outflow of aqueous humor through the uveoscleral pathway. It binds to FP receptors in the ciliary body, leading to relaxation of the ciliary muscle and remodeling of the extracellular matrix, which reduces resistance to aqueous humor outflow. This results in a significant reduction in intraocular pressure (IOP).

Pharmacodynamics: Latanoprost reduces IOP by approximately 25-35% in dogs and cats with glaucoma. The effect is dose-dependent and typically peaks 8-12 hours after administration. It also increases uveoscleral outflow, which is the primary mechanism in dogs and cats. In horses, it is used to treat uveitis-associated glaucoma and may have pro-inflammatory effects.

⚡ Pharmacokinetics Summary

Absorption: Latanoprost is absorbed through the cornea after topical ocular administration. The isopropyl ester prodrug is hydrolyzed by esterases in the cornea to the active acid form. Systemic absorption is minimal, but some may occur via the nasolacrimal duct.

Distribution: The active acid form distributes into the aqueous humor and ocular tissues. Systemic distribution is negligible due to rapid hydrolysis and low doses.

Metabolism: The prodrug is hydrolyzed to the active acid in the cornea and then metabolized by beta-oxidation in the liver and other tissues. The active acid is also metabolized to inactive metabolites.

Excretion: Metabolites are excreted primarily via the kidneys. In dogs, the elimination half-life of the active acid from plasma is short (approximately 17 minutes), but ocular effects persist for 24 hours.

Half-Life: Dogs: 17 minutes (plasma); ocular effects last 24 hours. Cats: not well-defined, but similar to dogs. Horses: not well-defined.

Bioavailability: Systemic bioavailability is low (<5%) after ocular administration due to corneal absorption and rapid metabolism.

Protein Binding: Approximately 80% bound to plasma proteins in humans; similar in animals.

Available Formulations & Strengths

Ophthalmic solution 0.005% (50 mcg/mL) (Topical ocular)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to latanoprost or any component of the formulation
Use in patients with active intraocular inflammation (e.g., uveitis) unless specifically indicated and monitored
Use in patients with known macular edema (in humans; caution in animals)

Warnings & Clinical Precautions:

May cause changes in iris pigmentation (heterochromia) with long-term use, especially in light-colored eyes
May cause eyelash growth and darkening of periocular skin
Use with caution in patients with a history of ocular inflammation or trauma
May cause bronchospasm in sensitive individuals (rare)
Do not administer to pregnant animals unless benefits outweigh risks; may cause abortion in some species
Use with caution in animals with compromised corneal epithelium
Monitor IOP regularly to assess efficacy

Adverse Effects & Reactions

Common:

Conjunctival hyperemia
Miosis
Blurred vision (transient)
Lacrimation
Ocular irritation or stinging

Serious / Severe:

Uveitis or exacerbation of intraocular inflammation
Cystoid macular edema (rare)
Iris pigmentary changes (cosmetic)
Corneal edema

Rare:

Bronchospasm
Systemic hypotension
Headache (in humans; not applicable)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Cholinergic agonists (e.g., pilocarpine)	Additive reduction in IOP; may be used in combination but may increase risk of ocular irritation	Moderate
Beta-blockers (e.g., timolol)	Additive IOP reduction; may be used in combination	Mild
Carbonic anhydrase inhibitors (e.g., dorzolamide)	Additive IOP reduction; may be used in combination	Mild
Corticosteroids (topical or systemic)	May increase IOP, counteracting the effect of latanoprost; monitor IOP	Moderate
NSAIDs (topical)	May reduce the ocular hypotensive effect; use with caution	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Ocular irritation
Conjunctival hyperemia
Miosis
Possible systemic effects if ingested (e.g., abdominal cramps, diarrhea)

Emergency Treatment Protocol: If ocular overdose occurs, flush the eye with saline. If ingested, treat symptomatically and supportively. There is no specific antidote.

Food Animal Withdrawal Times

Not approved for food animals; no withdrawal times established. Use in food animals is prohibited or requires extended withdrawal periods.

Storage, Handling & Regulatory Information

Storage Temperature: Store at 2-8°C (36-46°F) before opening; after opening, may be stored at room temperature (15-25°C) for up to 6 weeks.

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

Handling & Special Conditions: Protect from light. Keep the bottle tightly closed when not in use.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use (Xalatan).

Extra-Label (Off-Label) Use: In the US, latanoprost is FDA-approved for human use; in veterinary medicine, it is used extra-label under the Animal Medicinal Drug Use Clarification Act (AMDUCA) for dogs, cats, and horses. For food animals, extra-label use is prohibited if an approved animal drug exists, and withdrawal times must be established.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Latanoprost is a first-line treatment for glaucoma in dogs and cats due to its potent IOP-lowering effect and once-daily dosing. It is particularly effective in dogs with primary glaucoma. In cats, it is also effective but may cause more local irritation. In horses, it is used for uveitis-associated glaucoma, but caution is advised due to potential pro-inflammatory effects. It should be used with caution in animals with uveitis, as it may exacerbate inflammation. Regular monitoring of IOP and ocular health is essential. The drug is generally well-tolerated, but cosmetic changes in iris color may occur with long-term use.

References & Literature

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