Latanoprost: Prostaglandin F2α Analogue for Glaucoma
Latanoprost (Xalatan) is a prodrug prostaglandin F2α analogue that is hydrolysed in the cornea to its active acid form. It lowers intraocular pressure (IOP) by increasing uveoscleral outflow — the primary mechanism for IOP reduction.
First-line treatment for open-angle glaucoma and ocular hypertension. Administered as a single nightly drop. One of the most commonly prescribed glaucoma treatments worldwide.
Mechanism of Action
Stimulates FP (prostaglandin F) receptors in the ciliary body, increasing uveoscleral outflow (non-conventional aqueous outflow pathway). Does not significantly reduce aqueous production (unlike beta-blockers or carbonic anhydrase inhibitors). Reduces IOP by 25–35%.
Indications & Use
Open-angle glaucoma, ocular hypertension (elevated IOP without structural damage). First-line in most guidelines. Also used in secondary glaucomas. Administer once daily in the evening (evening dosing is more effective than morning).
Dosage
One drop in affected eye(s) once daily in the evening. More frequent application reduces the IOP-lowering effect (receptor down-regulation). Nasolacrimal occlusion after application reduces systemic absorption.
Side Effects
Local: conjunctival hyperaemia (most common — usually transient), iris pigmentation changes (irreversible brown pigmentation in mixed-colour irises — up to 33% over 5 years), eyelash growth (hypertrichosis — longer, thicker, darker lashes), periorbital skin darkening. Rare: macular oedema (aphakic/pseudophakic eyes).
Drug Interactions
Other prostaglandin analogues: generally avoid combining (no additive benefit, possible antagonism). Timolol (beta-blocker): common combination — additive IOP reduction. NSAIDs (topical): may reduce latanoprost efficacy.
Contraindications
Hypersensitivity to latanoprost or benzalkonium chloride (preservative). Caution in patients with aphakia or pseudophakia (macular oedema risk), inflammatory eye disease, previous viral keratitis. Contains benzalkonium chloride — remove contact lenses, reinsert after 15 minutes.
Frequently Asked Questions
Why does latanoprost change eye colour?
Latanoprost stimulates melanin production in the iris stroma, causing irreversible darkening of mixed-colour (hazel, blue-brown) irises. Blue eyes or uniformly brown eyes are rarely affected. This colour change is permanent and patients should be warned before starting.
Why must latanoprost be stored in the fridge before opening?
Unopened bottles require refrigeration (2–8°C) to maintain stability. Once opened, the bottle can be stored at room temperature (below 25°C) for up to 6 weeks.
Why is latanoprost administered in the evening?
Clinical studies show that evening dosing produces a greater 24-hour IOP reduction than morning dosing. This is thought to be related to the circadian rhythm of aqueous production and outflow pathways.
References
- EMA Xalatan SPC 2023
- EGS Guidelines Glaucoma 2020
- Camras CB et al. Ophthalmology 1996
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.