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:
- Keeping it on the bathroom counter-heat and moisture from showers degrade it fast
- Using it past 28 days after opening-even if it looks fine
- Touching the dropper to the eye or any surface
- Leaving it in a hot car or near a heater
- 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.
Can I refrigerate besifloxacin after opening?
You can, but it won’t extend the 28-day use window. Once opened, the clock starts ticking regardless of temperature. Refrigeration helps slow degradation slightly, but it doesn’t reset the clock. The manufacturer’s 28-day limit still applies.
What if I accidentally left my besifloxacin in the car all day?
If the temperature in your car exceeded 30°C (86°F), the medication likely lost potency. Even if it looks normal, don’t use it. Heat accelerates chemical breakdown. When in doubt, throw it out and get a new prescription.
Can I use besifloxacin for other eye infections besides pink eye?
No. Besifloxacin is only approved for bacterial conjunctivitis. It won’t work for viral or fungal infections, allergies, or dry eye. Using it for the wrong condition can delay proper treatment and increase resistance risk. Always get a diagnosis before using antibiotics.
Is it safe to share besifloxacin with someone else?
Never share eye drops. Even if the person has similar symptoms, their infection could be caused by a different bacteria or a virus. Sharing also risks cross-contamination. Each bottle is meant for one person only.
How do I know if my besifloxacin is still good after 28 days?
You can’t tell just by looking. Even if the solution appears clear and unchanged, its potency may have dropped below effective levels. The 28-day rule is based on lab testing-not appearance. Always discard after 28 days, no exceptions.
Mary Follero
November 20, 2025 AT 01:07Just finished a course of besifloxacin last week and I’m so glad I read this. I kept mine in the fridge after opening because I was paranoid it’d go bad. Turns out, I didn’t need to-but I also didn’t hurt anything. The 28-day rule is non-negotiable though. I tossed mine on day 27 just to be safe. Better safe than blind.
Also, never let the tip touch your eye. I learned that the hard way when I accidentally brushed it against my lash. Threw it out immediately. No regrets.
Will Phillips
November 22, 2025 AT 00:40They say 28 days but let me tell you something-pharma companies make this stuff to sell more bottles. I kept mine in my glove compartment for two weeks while I drove to Arizona and it was fine. I didn’t get sick. The FDA is just scared of lawsuits. You think they care about your eye or do they care about their quarterly profits?
Also why is the bottle amber? Because they don’t want you to see how much of it is just water and corporate greed. I’ve seen the inside of those vials. It’s all smoke and mirrors.
Arun Mohan
November 24, 2025 AT 00:14How quaint. You Americans treat eye drops like they’re artisanal kombucha. In Mumbai, we’ve been using topical antibiotics for decades without refrigeration, without fear, without a 28-day expiry obsession. The real issue? Overprescription. You don’t need besifloxacin for every red eye. Most conjunctivitis is viral. But your doctors are addicted to prescribing. And you? You’re addicted to following orders.
Also, the amber bottle? Cute. But UV degradation? That’s a lab myth. I’ve used expired drops for years. My eyes are fine. Your anxiety is the real infection.
Tyrone Luton
November 24, 2025 AT 17:57There’s something deeply poetic about how we treat medicine these days. We take a molecule-born in a lab, engineered to fight microscopic invaders-and we turn it into a sacred object. We fear its degradation like it’s a dying soul. We obsess over temperature, light, time.
But what if the real instability isn’t in the bottle? What if it’s in us? Our need to control, to measure, to follow rules written by corporations who’ve never held a crying child with pink eye? Maybe the drop doesn’t lose potency. Maybe we lose faith.
Still. I’ll follow the 28 days. Because sometimes, faith is just obedience with a prescription.
darnell hunter
November 25, 2025 AT 17:43It is imperative to adhere to the manufacturer's guidelines regarding the storage and temporal integrity of besifloxacin hydrochloride ophthalmic solution. Deviation from the specified parameters-namely, refrigeration prior to opening and a strict 28-day post-opening window-constitutes a violation of established pharmacological safety protocols. The risk of microbial contamination and therapeutic ineffectiveness is statistically significant and ethically indefensible.
Furthermore, the assertion that environmental exposure in a vehicle constitutes an absolute contraindication is empirically supported by peer-reviewed stability studies. Any deviation from these standards is not merely irresponsible-it is negligent.
Hannah Machiorlete
November 26, 2025 AT 01:49Ugh I hate when people act like this stuff is some magic potion. I left mine on the counter for 40 days because I was lazy and my eye got better anyway. Probably just got lucky. But now I feel guilty. Like I betrayed my own cornea or something.
Also why does everything have to be so dramatic? "Silent killer"? "Degradation"? It’s eye drops. Not plutonium.
Still. I bought a new one. Just in case. I’m a mess.
Bette Rivas
November 27, 2025 AT 14:43Let me expand on the degradation study cited in the post. The 2021 Journal of Ocular Pharmacology and Therapeutics paper used HPLC to quantify besifloxacin concentration under accelerated aging conditions. At 30°C and 75% relative humidity, degradation followed first-order kinetics with a half-life of approximately 21 days. Even at 25°C, the degradation rate was measurable at 0.18% per day, meaning by day 28, the active ingredient had dropped to 94.9% of original potency. While that may seem minor, in ophthalmic applications, the therapeutic window is narrow. A 5% reduction can push the concentration below the MIC for resistant strains like MRSA. That’s not theoretical-it’s documented in clinical failure reports. The 28-day limit isn’t arbitrary. It’s the result of rigorous stability testing under ICH guidelines. Don’t gamble with your vision.
Also, the amber bottle isn’t just for show. It blocks wavelengths below 450nm, which are the primary drivers of photodegradation. Clear bottles would require preservatives at higher concentrations, which could cause corneal toxicity. So yes, keep it in the carton. Even if you think you’re being careful.
prasad gali
November 27, 2025 AT 21:07From a pharmaceutical standpoint, the 28-day post-opening window is a conservative estimate derived from microbial challenge testing per USP <61> and <62>. The real concern isn’t just potency loss-it’s biofilm formation on the dropper tip. Pseudomonas aeruginosa and Staphylococcus epidermidis can colonize the tip within 72 hours of ambient exposure, especially in humid environments. The bottle isn’t sterile after first use. It’s a vector. That’s why the FDA mandates single-use discard. Refrigeration doesn’t mitigate biofilm. Only time and contamination control do.
Also, the mention of UV degradation is correct but incomplete. Besifloxacin undergoes photolytic cleavage at the C-8 position, producing a cytotoxic quinone derivative. That’s why even ambient indoor lighting contributes to breakdown. The amber bottle reduces this by 87%. Still-not perfect. Keep it in the dark.
Paige Basford
November 28, 2025 AT 15:19Okay I’m gonna be real-I totally left mine in my car for a day because I was rushing to work. I was like ‘eh it’ll be fine’ and then I panicked and googled it. Turns out I should’ve just tossed it. But here’s the thing-I didn’t get worse. My eye just… got better on its own. So now I’m confused. Is it the drops? Or is it my body? Or am I just lucky?
Also I keep mine in my purse now. And I always wash my hands. I think I’m doing okay. Maybe I’m overthinking it. But I’m also not risking it again. You know? Like… I care now.
Also can we talk about how weird it is that we’re all so scared of eye drops? Like, it’s just a liquid. But we treat it like it’s a baby. 🤔
Ankita Sinha
November 28, 2025 AT 23:17Wait so if I refrigerate after opening, does it slow down the degradation? Or is it just a myth? I’ve been doing it because I read somewhere it helps. But now I’m not sure. I mean, if the clock starts ticking at day one, why even bother? But I also don’t want my drops to go bad early. This is so confusing.
Also-has anyone tried using a clean eyedropper from a pharmacy to transfer the liquid to a smaller sterile container? Like to avoid touching the tip? I feel like that could help. But I’m scared I’ll mess it up. Anyone tried this?
Kenneth Meyer
November 30, 2025 AT 11:26There’s a quiet tragedy in how we treat medicine now. We treat it like a machine that must be perfectly calibrated, when in truth, our bodies are far more resilient than our manuals suggest. The 28-day rule is a shield against liability, not a law of nature. The molecule degrades. The bacteria adapt. We fear both.
But what if the real lesson isn’t in the bottle? What if it’s in the way we’ve learned to distrust our own bodies? We don’t wait to see if the infection clears-we reach for another bottle. We don’t listen to our eyes-we read the label.
Still. I follow the rules. Because sometimes, humility means trusting the science even when you don’t fully understand it.
Donald Sanchez
November 30, 2025 AT 17:06bro i just put my besifloxacin in my back pocket for 3 days and it was fine 😎 also i reused the bottle for my cat’s eye infection (she had pink eye too) and she’s good now. also i didn’t wash my hands once. no cap. pharma is just trying to sell more bottles. i saved 80 bucks. also i think the 28 day thing is fake. i checked the bottle and it looked the same. why do they make us feel bad? 🤷♂️🔥