Latanoprost

• Open-angle glaucoma
• Ocular hypertension
• First-line IOP reduction
• Normal-tension glaucoma

Latanoprost is a prostaglandin F2α analog used to reduce elevated intraocular pressure in patients with open-angle glaucoma or ocular hypertension. As a first-line treatment for glaucoma, it provides effective IOP reduction with once-daily dosing and a favorable side effect profile compared to older glaucoma medications.

Mechanism of Action

Latanoprost is a prodrug that is hydrolyzed by corneal esterases to its biologically active acid form. The active drug is a selective prostanoid FP receptor agonist that reduces intraocular pressure primarily by increasing uveoscleral outflow, the secondary pathway for aqueous humor drainage. Unlike beta-blockers and carbonic anhydrase inhibitors, latanoprost does not significantly reduce aqueous humor production.

The increased uveoscleral outflow is thought to result from prostaglandin-induced remodeling of the extracellular matrix in the ciliary muscle and sclera, reducing resistance to aqueous outflow through these tissues. This mechanism provides sustained IOP reduction that is maintained with long-term therapy.

Available Formulations

Latanoprost (Xalatan) is available as a 0.005% (50 mcg/mL) ophthalmic solution. Generic formulations are widely available. Preservative-free formulations and combination products with timolol (Xalacom) or netarsudil (Rocklatan) are also available for patients requiring combination therapy or those sensitive to preservatives. The medication requires refrigeration until opened; once opened, it may be stored at room temperature for up to 6 weeks.

FDA-Approved Indications

Latanoprost is FDA-approved for the reduction of elevated intraocular pressure in patients with open-angle glaucoma and ocular hypertension. It is considered a first-line treatment option due to its efficacy, once-daily dosing, and favorable systemic side effect profile. The medication is effective across various types of open-angle glaucoma including primary open-angle glaucoma, normal-tension glaucoma, and pseudoexfoliative glaucoma.

Dosing Guidelines

The recommended dose is one drop in the affected eye(s) once daily in the evening. Using the medication more frequently than once daily may decrease its IOP-lowering effect. If one dose is missed, treatment should continue with the next dose as scheduled. If used with other topical ophthalmic medications, they should be administered at least 5 minutes apart.

IOP-Lowering Efficacy

Latanoprost typically reduces IOP by 25-35% from baseline, which is generally superior to beta-blockers and other non-prostaglandin glaucoma medications. Maximum IOP reduction is usually achieved after 3-4 weeks of therapy. The once-daily evening dosing takes advantage of the circadian pattern of IOP, which is typically highest in the early morning.

Important Safety Considerations

Latanoprost may gradually increase pigmentation of the iris, periorbital tissue (eyelid), and eyelashes. The iris color change occurs slowly and may be permanent, most notable in patients with mixed eye colors. Eyelash changes (length, thickness, number, pigmentation) are generally reversible upon discontinuation. Rarely, latanoprost may cause reactivation of herpes simplex keratitis and should be used with caution in patients with a history of herpetic keratitis. Macular edema, including cystoid macular edema, has been reported, particularly in patients with risk factors.

Drug Interactions

NSAIDs may reduce the IOP-lowering effect when used concomitantly. If used with other topical ophthalmic medications, administer at least 5 minutes apart. Precipitation may occur if latanoprost is mixed with thimerosal-containing ophthalmic products; administer at least 5 minutes apart.

Special Populations

Safety and efficacy in pediatric patients have not been established. Use during pregnancy only if clearly needed (pregnancy category C). Remove contact lenses before administration; they may be reinserted 15 minutes after dosing. Patients should be informed about the potential for permanent eye color change before initiating therapy.

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