Glaucoma is a progressive eye disease characterized by damage to the optic nerve, often caused by elevated intraocular pressure (IOP). Reducing IOP is the only proven method to slow disease progression and prevent irreversible vision loss. Latanoprost and latanoprostene bunod are first-line prostaglandin analog medications used to lower IOP in patients with open-angle glaucoma or ocular hypertension. Latanoprost is a long-established, generic drug, while latanoprostene bunod is a newer, chemically modified molecule. Both are administered as once-daily eye drops and function as prodrugs, becoming active only after being metabolized by the eye.
Distinct Mechanisms for Lowering Intraocular Pressure
The fundamental difference between these two treatments lies in how they facilitate the drainage of fluid from the eye. Latanoprost is a prodrug converted into latanoprost acid, the active compound. Latanoprost acid works by binding to prostaglandin F (FP) receptors in the ciliary muscle, enhancing the flow of aqueous humor through the uveoscleral pathway, the unconventional outflow route.
Latanoprostene bunod (LBN) has a unique chemical structure that grants it a dual mechanism of action, targeting both major outflow pathways. Once instilled, LBN is metabolized into two active components: latanoprost acid and a nitric oxide (NO)-donating component. The latanoprost acid moiety increases drainage via the uveoscleral pathway.
The NO-donating component distinguishes LBN by releasing nitric oxide into the eye’s tissues. Nitric oxide causes relaxation of the smooth muscle cells within the trabecular meshwork, the eye’s primary drainage system. By simultaneously increasing outflow through both the uveoscleral and trabecular meshwork routes, LBN provides a more comprehensive approach to reducing fluid resistance.
Comparative Reduction of Eye Pressure
Clinical trials have consistently demonstrated that latanoprostene bunod (LBN) provides a statistically greater reduction in IOP compared to latanoprost. LBN has been shown to lower mean diurnal IOP by an additional 1 to 1.23 mmHg beyond the reduction achieved by latanoprost. This additional pressure lowering is often referred to as a therapeutic gain.
Studies indicated that a significantly greater proportion of patients using LBN achieved a target IOP of 18 mmHg or lower compared to those treated with latanoprost. This enhanced efficacy is attributed directly to LBN’s ability to utilize the trabecular meshwork pathway in addition to the uveoscleral pathway.
Achieving even a small additional reduction in IOP has significant long-term implications for the patient’s prognosis. Glaucoma progression is closely linked to the magnitude of pressure reduction, meaning a greater drop in IOP is associated with a lower risk of visual field loss. The superior IOP-lowering effect suggests that LBN may be a beneficial option for individuals who require lower pressures or who have not reached their target on latanoprost alone.
Differences in Safety Profile and Practical Use
Both latanoprost and latanoprostene bunod share common class-related ocular side effects typical of prostaglandin analogs. These effects include conjunctival hyperemia (temporary redness of the eye), darkening of the iris, and increased growth and thickness of the eyelashes. The incidence of conjunctival hyperemia was comparable between the two medications.
A notable difference in the safety profile is the reported incidence of pain upon instillation. Some studies indicate that the LBN formulation may cause a numerically higher rate of instillation site pain, though adverse events remain mostly mild to moderate. Both drugs maintain the convenience of once-daily dosing, typically administered in the evening.
The most substantial difference in practical use is the cost. Latanoprost is widely accessible as an inexpensive generic formulation. Latanoprostene bunod (Vyzulta) is a newer, patented drug, making it significantly more expensive. Due to the higher cost, LBN is often reserved for patients who need the additional IOP lowering provided by the dual mechanism or for those whose glaucoma progresses despite generic latanoprost treatment.