Latanoprost is a prescription eye drop belonging to the class of prostaglandin analogs. It is primarily used to manage elevated pressure within the eye, known as intraocular pressure. High eye pressure is a factor in the progression of conditions like open-angle glaucoma and ocular hypertension. Correct storage conditions are important to ensure the active ingredient remains effective.
Ideal Storage for Unopened Medication
Long-term storage for latanoprost requires cold temperatures to maintain chemical stability. Manufacturers instruct that unopened bottles must be kept under refrigeration, specifically between 2°C and 8°C (36°F and 46°F). This cool environment preserves the integrity of the active molecule over its full lifespan. When stored continuously under refrigeration, the medication remains effective until the printed expiration date.
This cold storage protects the drug from degradation caused by heat and light. The bottle must be protected from freezing, as this compromises the solution’s integrity. For proper long-term preservation, the medication should be returned to the refrigerator immediately after being dispensed.
Stability Window at Room Temperature
While refrigeration is the standard for long-term storage, an unopened bottle of latanoprost has a limited stability window at room temperature. This temporary allowance accounts for temperature excursions during shipping and transit. Latanoprost is stable at temperatures up to 40°C (104°F) for a period not exceeding 8 days.
If an unopened bottle is accidentally left out of the refrigerator, it is generally acceptable for use if exposed to normal room temperatures for less than one week. This short-term stability is not intended for routine storage but safeguards against brief temperature fluctuations. Once the bottle is opened, the storage rules change immediately, overriding the long-term expiration date.
Handling and Storage After Opening
Once the seal of the latanoprost bottle is broken, the primary storage recommendation shifts from refrigeration to controlled room temperature. After opening, the medication should be stored at temperatures up to 25°C (77°F). This change makes daily application more convenient for the patient.
The most important rule after opening is the discard date, set at 6 weeks (42 days), regardless of the amount remaining. This timeline is based on the drug’s chemical stability and the risk of microbial contamination. Every time the dropper tip is exposed, there is a possibility of introducing bacteria from the environment or the eye surface.
Preservatives, such as benzalkonium chloride, inhibit bacterial growth but have a limited effective period once the bottle is opened. Using the drops beyond the 6-week window increases the risk of introducing an eye infection. Marking the date of first opening directly on the bottle label ensures this expiration timeline is followed.
Defining Safe Storage Temperatures
In pharmaceuticals, “room temperature” refers to the standard known as Controlled Room Temperature (CRT). This range is defined as 20°C to 25°C (68°F to 77°F). Brief temperature excursions are permitted within a wider range of 15°C to 30°C (59°F to 86°F), such as during transport.
It is important to avoid temperature extremes outside of this defined range for long periods. Exposure to excessive heat, defined as any temperature above 40°C (104°F), causes the active drug to degrade rapidly. Allowing the solution to freeze can disrupt the formulation, leading to a loss of effectiveness. Storing the medication in a location protected from direct sunlight, such as a cool cabinet, helps maintain the product’s quality.