Introduction
Xalatan (latanoprost) is a prostaglandin analog ophthalmic solution developed by Pfizer Inc. for the reduction of elevated intraocular pressure (IOP) in patients with open-angle glaucoma and ocular hypertension. First approved by the FDA in 1996, it has become a first-line treatment option due to its efficacy, once-daily dosing, and generally favorable side effect profile.
Mechanism of Action
Latanoprost is a prostaglandin F2α analog that works primarily by increasing uveoscleral outflow of aqueous humor. It acts as a selective FP prostanoid receptor agonist, which leads to remodeling of the extracellular matrix in the ciliary muscle, reducing resistance to aqueous humor outflow through the uveoscleral pathway. This mechanism results in a significant reduction of intraocular pressure without substantially affecting aqueous production.
Indications
- Reduction of elevated intraocular pressure in patients with open-angle glaucoma
- Ocular hypertension
- May be used as monotherapy or in combination with other intraocular pressure-lowering medications
Dosage and Administration
Standard dosing: One drop (approximately 1.5 mcg) in the affected eye(s) once daily in the evening Route: Topical ophthalmic administration Special populations:- Hepatic impairment: No dosage adjustment necessary
- Renal impairment: No dosage adjustment necessary
- Pediatric patients: Safety and effectiveness in pediatric patients have not been established
- Geriatric patients: No dosage adjustment necessary
Pharmacokinetics
Absorption: Latanoprost is absorbed through the cornea, where the isopropyl ester prodrug is hydrolyzed to the active acid Distribution: Minimal systemic exposure; the acid reaches the systemic circulation primarily through the conjunctival and nasal mucosa Metabolism: Undergoes rapid hydrolysis in the cornea to the biologically active acid form; systemically metabolized primarily by fatty acid β-oxidation in the liver Elimination: Plasma half-life is approximately 17 minutes; eliminated primarily in urine (88%) within 24 hours after both hepatic and extrahepatic metabolismContraindications
- Hypersensitivity to latanoprost or any component of the formulation
- Patients with active intraocular inflammation (iritis/uveitis)
- Contraindicated in patients with known risk factors for macular edema, including aphakic patients, pseudophakic patients with torn posterior lens capsule, or patients with known risk factors for macular edema
Warnings and Precautions
- May cause permanent changes to iris pigmentation, eyelid skin darkening, and eyelash changes (increased length, thickness, pigmentation, and number of lashes)
- Use with caution in patients with a history of intraocular inflammation
- May cause macular edema, including cystoid macular edema
- Use with caution in patients with compromised corneas or corneal epithelial defects
- Contact lenses should be removed prior to administration and may be reinserted 15 minutes after instillation
- Bacterial keratitis has been reported with the use of multiple-dose containers
Drug Interactions
- No clinically significant pharmacokinetic drug interactions have been identified
- Theoretical potential for additive effect when used with other prostaglandin analogs
- Concomitant use with eye drops containing thimerosal may cause precipitation and should be separated by at least 5 minutes
Adverse Effects
Common (≥1-10%):- Ocular hyperemia (35-45%)
- Foreign body sensation
- Ocular pruritus
- Blurred vision
- Burning/stinging
- Iris pigmentation changes (7-20%, typically developing over 3-12 months)
- Eyelash changes (increased length, thickness, and number)
- Macular edema
- Uveitis
- Keratitis
- Eyelid skin darkening
- Intraocular inflammation
Monitoring Parameters
- Intraocular pressure measurement at regular intervals
- Regular ophthalmic examinations including visual field testing
- Monitoring for changes in iris pigmentation
- Assessment of periocular skin and eyelash changes
- Evaluation for signs and symptoms of intraocular inflammation
- Monitoring for macular edema in at-risk patients
Patient Education
- Administer one drop in affected eye(s) once daily in the evening
- Do not touch dropper tip to any surface to avoid contamination
- Remove contact lenses before administration and wait 15 minutes before reinsertion
- May cause permanent brown pigmentation of the iris, eyelid skin darkening, and eyelash changes
- May gradually change eye color by increasing the amount of brown pigment in the iris
- Report any eye inflammation, infection, or trauma to healthcare provider
- Do not use while wearing contact lenses
- Wait at least 5 minutes between instilling different eye drops
- Discard bottle 4 weeks after opening
References
1. Alm A, Grierson I, Shields MB. Side effects associated with prostaglandin analog therapy. Surv Ophthalmol. 2008;53 Suppl1:S93-S105. 2. FDA Prescribing Information: Xalatan (latanoprost) ophthalmic solution. 2021. 3. Camras CB, Alm A. Initial treatment for open-angle glaucoma--prostaglandin/analogs. Surv Ophthalmol. 2008;53 Suppl1:S9-S15. 4. van der Valk R, Webers CA, Schouten JS, et al. Intraocular pressure-lowering effects of all commonly used glaucoma drugs: a meta-analysis of randomized clinical trials. Ophthalmology. 2005;112(7):1177-1185. 5. Watson PG, Barnett MF, Parker V, Haybittle J. A 7-year prospective comparative study of three topical β blockers in the management of primary open-angle glaucoma. Br J Ophthalmol. 2001;85(8):962-968. 6. The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol. 2000;130(4):429-440.