Latanoprost is a prescription eye drop used to lower elevated eye pressure in people with open-angle glaucoma or ocular hypertension. It belongs to a class of drugs called prostaglandin analogs and is one of the most commonly prescribed glaucoma medications worldwide, sold under the brand name Xalatan among others. Most people using it can expect a pressure reduction of roughly 20% to 36%, depending on their baseline levels and how they respond to treatment.
How Latanoprost Lowers Eye Pressure
Your eye constantly produces a fluid called aqueous humor, which normally drains out through two pathways. In glaucoma and ocular hypertension, that drainage slows down, and pressure builds inside the eye. Left unchecked, the rising pressure damages the optic nerve and can gradually steal your vision.
Latanoprost works by opening up one of those drainage routes, called the uveoscleral pathway. It triggers a remodeling process in the tissue surrounding that pathway, loosening the connective fibers so fluid passes through more easily. The effect begins within a few hours of the first drop, but the full pressure-lowering benefit builds over days to weeks as the tissue remodeling progresses. In clinical comparisons, 63% of patients on latanoprost reached their target pressure after six months, compared to 39% of patients on timolol, a commonly used beta-blocker eye drop. Latanoprost also produced lower average pressures overall: about 20.8 mmHg versus 23.4 mmHg for timolol at the six-month mark.
How to Use It
The standard dose is one drop in the affected eye once daily in the evening. Nighttime dosing is deliberate: the drug works best when applied at that time, and using it more than once a day can actually reduce its effectiveness or even cause pressure to rise. You should never double up on doses or combine latanoprost with another prostaglandin-type drop for the same reason.
If you wear contact lenses, remove them before putting the drop in and wait at least 15 minutes before reinserting them. The preservatives in most formulations can be absorbed by soft lenses and irritate your eyes over time.
Storage Requirements
Latanoprost is sensitive to heat. For the standard Xalatan formulation, keep unopened bottles in the refrigerator. Once you open a bottle, you can store it at room temperature (around 68 to 77°F) for up to six weeks. After six weeks, discard whatever is left, even if the bottle isn’t empty. Some newer single-dose formulations have slightly different rules, so check the packaging, but the general principle holds: keep it cool and don’t use it past its window.
Side Effects to Expect
The most distinctive side effects of latanoprost involve cosmetic changes to the eye and surrounding skin. Over months to years of use, the iris can gradually darken in color. This is most noticeable in people with mixed-color irises: blue-brown, green-brown, gray-brown, or yellow-brown eyes. The change happens because latanoprost stimulates melanin production in the iris, and it is typically permanent even after stopping the medication. People with uniformly brown or blue eyes are less likely to notice a shift.
Many users also develop longer, thicker, and darker eyelashes on the treated eye. This effect is so reliable that a related compound was eventually developed and marketed specifically as an eyelash-growth product. Darkening of the eyelid skin can also occur. Like the iris change, eyelash and eyelid changes may not reverse after discontinuation, and they only affect the eye receiving the drops. If you’re treating just one eye, you may notice an asymmetry between the two sides over time.
The most common short-term side effect is eye redness (hyperemia). In clinical trials comparing latanoprost to timolol, redness was reported roughly nine times more often in the latanoprost group. Eye irritation, stinging on application, and a feeling of something in the eye are also reported, though these tend to be mild and often improve with continued use.
Who Should Use Caution
Latanoprost is specifically approved for open-angle glaucoma and ocular hypertension. It is not a treatment for all forms of glaucoma. People with a history of inflammatory eye conditions like uveitis, or those who have had certain eye surgeries that affect the lens capsule, may face a higher risk of swelling in the central part of the retina (the macula). Your eye doctor will weigh these factors before prescribing it.
Because the iris color change is irreversible, people who are treating only one eye should be informed about the possibility of ending up with two different-colored eyes. This doesn’t affect vision, but it’s a cosmetic consideration worth knowing about before starting treatment.
What Long-Term Use Looks Like
Glaucoma is a chronic condition, and latanoprost is typically a long-term or lifelong medication. The good news is that it maintains its pressure-lowering effect well over time for most people, and its once-daily evening dosing makes it easier to stick with than drops that require two or three applications a day. Regular eye pressure checks, usually every few months, help confirm the medication is still doing its job. If latanoprost alone doesn’t bring your pressure down far enough, your doctor may add a second type of drop rather than switching you off latanoprost entirely, since it targets a different drainage pathway than most other glaucoma medications.