A Guide to Besifloxacin Storage and Stability

When you’re prescribed besifloxacin eye drops, it’s not just about using them correctly-it’s about keeping them effective. If you store them wrong, you could end up with a bottle that doesn’t work at all. And that’s not just a waste of money; it could mean your infection doesn’t clear up, or worse, gets worse.

What Is Besifloxacin?

Besifloxacin is a fluoroquinolone antibiotic made specifically for the eye. It’s used to treat bacterial conjunctivitis-commonly known as pink eye-caused by susceptible strains of bacteria like Staphylococcus aureus, Streptococcus pneumoniae, and Hemophilus influenzae. Unlike some other antibiotic eye drops, besifloxacin is designed to stay active in the eye longer, which means fewer doses per day. But that doesn’t mean it’s forgiving when it comes to storage.

The active ingredient, besifloxacin hydrochloride, is sensitive to temperature, light, and moisture. Even small changes can break down the molecule and reduce its ability to kill bacteria. That’s why the manufacturer, Bausch + Lomb, gives very specific instructions for handling the product.

Recommended Storage Conditions

Before you open the bottle, store it in the refrigerator between 2°C and 8°C (36°F to 46°F). That’s standard for many eye medications. Don’t freeze it. Freezing can damage the solution’s structure and cause crystals to form, making it unsafe to use.

Once you open the bottle, you can keep it at room temperature-up to 25°C (77°F)-for up to 28 days. That’s the key number: 28 days. After that, even if there’s liquid left, throw it out. The FDA and the manufacturer both agree: beyond 28 days, the risk of contamination and potency loss rises sharply.

Keep the bottle tightly closed when not in use. Exposure to air introduces bacteria and moisture, which can grow inside the dropper tip. That’s why you should never let the tip touch your eye, eyelid, or any surface. If it does, discard the bottle immediately. No exceptions.

Why Stability Matters

Besifloxacin degrades faster than you might think. In a 2021 study published in the Journal of Ocular Pharmacology and Therapeutics, researchers tested stored besifloxacin under different conditions. When kept at 30°C (86°F) and exposed to light, the concentration dropped by 15% in just 14 days. At room temperature in the dark, it held up better-but still lost 5% by day 28.

That 5% might sound small, but in an antibiotic, even minor potency loss can mean the difference between killing bacteria and letting them survive. Surviving bacteria can multiply and become resistant. That’s how antibiotic resistance starts-not just from overuse, but from using weakened doses.

Light exposure is another silent killer. Besifloxacin is sensitive to UV and even strong indoor lighting. That’s why the bottle is made of amber plastic. It blocks most harmful wavelengths. But if you leave it on a sunny windowsill or in a bright bathroom cabinet, you’re still risking degradation. Always keep it in its original carton when not in use.

What Happens If You Use Expired or Improperly Stored Besifloxacin?

Using degraded besifloxacin won’t necessarily make you sick right away. But it won’t fix your infection either. You might notice:

• Your redness or discharge doesn’t improve after 2-3 days
• Your symptoms come back after stopping the drops
• Your eye feels worse instead of better

These aren’t side effects-they’re signs the medication failed. If this happens, don’t just reach for another bottle. See your doctor. You might need a different antibiotic, or your infection could have spread.

Also, never use besifloxacin past its printed expiration date, even if it’s been stored perfectly. The expiration date is based on stability testing under controlled conditions. Once it passes, there’s no guarantee the drug still works.

Traveling With Besifloxacin

If you’re flying or going on a trip, you need a plan. Airplane cabins can get hot, especially near windows. Don’t leave your eye drops in your checked luggage-temperatures in cargo holds can drop below freezing or rise above 40°C (104°F).

Carry your besifloxacin in your carry-on. Keep it in the original carton. If you’re going somewhere hot, use a small insulated pouch with a cold pack. Just make sure the cold pack doesn’t touch the bottle directly-wrap it in a cloth. You don’t want condensation forming on the bottle or cap.

And never leave it in a car. Even in winter, a parked car can turn into an oven. In summer? It’s a sauna. One day in a hot car can ruin a bottle.

How to Tell If Besifloxacin Has Gone Bad

Before each use, check the solution. Look for:

• Cloudiness or particles floating in the liquid
• Color change-besifloxacin should be clear and slightly yellowish
• Unusual odor or a strange taste (don’t taste it, but if you notice a foul smell when opening, that’s a red flag)
• Leakage or damage to the dropper tip

If you see any of these, throw it out. Don’t risk it. The cost of a new bottle is nothing compared to the cost of a worsening eye infection.

Disposal Guidelines

Don’t flush besifloxacin down the toilet or sink. That can contaminate water systems. Instead, take unused or expired bottles to a pharmacy drop-off program. Many pharmacies, including CVS, Walgreens, and local community centers, have medication take-back bins.

If no take-back program is available, mix the remaining liquid with an unappealing substance like coffee grounds or cat litter. Put it in a sealed plastic bag and throw it in the trash. Remove or black out the label to protect your privacy.

Common Mistakes to Avoid

Here are the most frequent errors people make with besifloxacin:

1. Keeping it on the bathroom counter-heat and moisture from showers degrade it fast
2. Using it past 28 days after opening-even if it looks fine
3. Touching the dropper to the eye or any surface
4. Leaving it in a hot car or near a heater
5. Assuming refrigeration extends the 28-day window after opening

Refrigeration only helps before opening. Once opened, room temperature is fine, but the clock starts ticking at day one. Don’t think storing it cold after opening gives you extra time. It doesn’t.

Final Checklist for Safe Use

Before each use, ask yourself:

• Is the bottle within 28 days of opening?
• Is the solution clear and slightly yellow?
• Is the dropper tip clean and undamaged?
• Have I kept it away from direct sunlight and heat?
• Did I wash my hands before applying?

If you answered yes to all, you’re good to go. If any answer is no, get a new bottle. Your eyes deserve better than guesswork.