The storage requirements for fluorescein are not universal and depend entirely on the specific formulation being used. For instance, dry ophthalmic strips are generally stable at room temperature, while some combination eye drops containing an anesthetic may require refrigeration to maintain the potency of all ingredients. Always consult the manufacturer's label for precise instructions, as improper storage can affect the product's stability and effectiveness.
The short answer: It depends on the product
There is no single rule for fluorescein storage. Healthcare professionals and patients must check the specific product label, as storage conditions like temperature, light exposure, and humidity are critical for preserving the medication's integrity. Factors like whether the fluorescein is a single agent, part of a combination product, or in a dry versus liquid form all dictate its ideal storage environment.
Storage for Different Fluorescein Formulations
Ophthalmic Eye Drops
For eye drops, the presence of other medications in a combination formula is often the deciding factor for refrigeration. Solutions like Proparacaine and Fluorescein are a prime example. While the fluorescein itself might be stable at warmer temperatures, the proparacaine anesthetic requires cold storage to preserve its effectiveness. These types of refrigerated drops can typically be kept at room temperature for a limited period (e.g., up to one month) before needing to be discarded. Other combination drops, such as those with benoxinate, also require refrigeration.
Ophthalmic Strips
Unlike liquid solutions, fluorescein sodium ophthalmic strips are a dry, solid-state product. As a result, they do not require refrigeration and are generally stored at room temperature. Protecting them from moisture and excessive heat is recommended to maintain their integrity and ensure proper performance. Each strip is individually packaged for sterility, and the packaging should remain sealed until just before use.
Fluorescein Injections
Fluorescein injections, used for procedures like angiography, have distinct storage guidelines. These sterile, injectable solutions are typically stored at USP Controlled Room Temperature, which is between 20° to 25°C (68° to 77°F). Manufacturers explicitly state that fluorescein injections should not be frozen. Once a single-dose vial is opened, any unused portion must be discarded to maintain sterility.
Fluorescein Powder and Repackaged Solutions
Pure fluorescein powder, used in laboratory settings or for compounding, should be stored in a cool, dry place and protected from light and moisture. For certain clinical needs, a pharmacist may repackage a single-use vial of fluorescein injection into smaller doses. In such cases, studies have shown that the repackaged syringes can be refrigerated for a short period (e.g., 7 days) without compromising potency or sterility. However, this is a special procedure for clinical use, not for general patient practice.
Key Factors Influencing Fluorescein Storage
- Formulation Composition: The most important factor is what the fluorescein is combined with. Combination eye drops with temperature-sensitive drugs like anesthetics require refrigeration, while fluorescein alone is often fine at room temperature.
- State of Matter: The form of the fluorescein—whether it's a dry powder, an ophthalmic strip, or an aqueous solution—dictates its storage needs. Dry forms are less susceptible to degradation than liquid solutions.
- Light and Heat Sensitivity: Many fluorescein products, regardless of their specific formulation, are sensitive to prolonged exposure to light and heat. This is why they are often supplied in dark containers and require storage in a cool, dark place.
- Microbial Contamination: Liquid preparations, especially once opened, risk microbial contamination. Refrigeration can slow microbial growth, and manufacturers specify discard dates (e.g., 28 days for many eye drops) to minimize risk.
A Comparison of Fluorescein Storage Requirements
| Formulation | Typical Storage | Refrigeration Needed? | Important Note |
|---|---|---|---|
| Dry Ophthalmic Strips | Room Temperature | No | Keep away from heat and moisture. |
| Combination Eye Drops (e.g., with proparacaine) | Refrigerated | Yes (typically 2-8°C) | Can be stored at room temp for up to one month. |
| Single-Agent Eye Drops (formulation dependent) | Room Temperature | No | Protect from light and heat. |
| Fluorescein Injections | Controlled Room Temperature (20-25°C) | No | Do not freeze; discard unused portions. |
| Fluorescein Powder | Cool, Dry Place | No | Protect from light, humidity, and heat. |
Best Practices for Handling Fluorescein
- Read the Label: Always follow the specific storage instructions provided on the packaging by the manufacturer. This is the most reliable source of information.
- Protect from Elements: Store all fluorescein products away from direct sunlight, excessive heat, and moisture. This is especially crucial for liquid formulations and powders.
- Mind Expiration Dates: Pay close attention to the expiration date on the packaging. For multi-dose eye drops, note the specific 'use-by' or 'discard after opening' date, as it is often shorter than the overall expiration date.
- Proper Disposal: Dispose of expired or unused fluorescein products as per the manufacturer's or local regulations. This is particularly important for single-dose injections where any leftover solution must be discarded.
- Ensure Sterility: For ophthalmic solutions, avoid touching the dropper tip to any surface, including the eye, to prevent contamination.
Conclusion
The notion that all fluorescein requires refrigeration is a common misconception. The correct storage method for fluorescein is highly dependent on its specific product formulation. While certain combination eye drops mandate cold storage to protect sensitive ingredients, dry strips and injections are typically stable at controlled room temperature, provided they are kept away from light and excessive heat. Adhering to the manufacturer's guidelines for storage and handling is essential for ensuring the product's safety, potency, and effectiveness. A quick check of the label is always the best course of action before storing any fluorescein product.
For more detailed information on specific products, always consult official product inserts, such as those found on regulatory agency websites like the FDA. For example, for AK-FLUOR® fluorescein injection, the official prescribing information outlines the correct storage conditions(https://www.fffenterprises.com/assets/downloads/product-information/long-grove-pharmaceuticals/pi-AK-FLUOR.pdf).
