Besifloxacin: Uses, Dosage, Side Effects and Interactions

Besifloxacin is a fourth-generation fluoroquinolone antibiotic specifically developed for ophthalmic (eye) use. Approved by the FDA in 2009, it has become an important option for treating bacterial eye infections, especially as antibiotic resistance becomes a growing concern. This article provides a deep dive into the uses, recommended dosages, side effects, and potential interactions of besifloxacin, helping patients and professionals alike understand how to use it safely and effectively.

Uses of Besifloxacin

Besifloxacin stands out for its potent antibacterial action against a wide range of bacteria responsible for eye infections. Unlike older fluoroquinolones, it is formulated exclusively for topical ophthalmic application, giving it a unique role in managing ocular infections.

Indication	Target Organisms	Unique Attributes	Sources
Bacterial conjunctivitis	Gram-positive and Gram-negative bacteria, including drug-resistant strains	Approved only for ophthalmic use; broad-spectrum; effective against resistant bacteria	1, 4, 5, 12, 13
Bacterial keratitis	Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Corynebacterium spp.	Off-label for keratitis; studied for safety in keratitis patients	9, 12, 4
Surgical prophylaxis	Post-cataract and LASIK surgery	Shown safe as perioperative prophylactic	11

Table 1: Main Clinical Uses of Besifloxacin

Targeted Ocular Infections

Besifloxacin is primarily indicated for the treatment of bacterial conjunctivitis, which is an infection of the outer membrane of the eye and the inner eyelid. It is effective against both Gram-positive and Gram-negative pathogens, including those resistant to other antibiotics. This is due to its dual inhibition of DNA gyrase and topoisomerase IV, two key enzymes necessary for bacterial DNA replication 4 12.

• Bacterial Conjunctivitis: Besifloxacin has demonstrated higher clinical resolution and bacterial eradication rates in clinical studies compared to placebo (vehicle) 1 4 5 6 7 13.
• Bacterial Keratitis: While not its primary indication, besifloxacin has been used off-label in the treatment of bacterial keratitis (corneal infections), showing good tolerability and safety 9.
• Surgical Prophylaxis: Used as a perioperative antibacterial prophylaxis in cataract and LASIK surgeries, besifloxacin has a favorable safety profile and similar surgical outcomes compared to moxifloxacin 11.

Broad-Spectrum and Resistant Pathogen Coverage

A major advantage of besifloxacin is its broad-spectrum activity, particularly its high potency against drug-resistant ocular bacterial strains. This includes methicillin-resistant Staphylococcus aureus (MRSA) and strains with mutations conferring resistance to earlier fluoroquinolones 4 12 14. Its molecular structure allows for effective action even in the presence of mutations in bacterial enzymes that often lead to resistance 14.

Exclusively Topical Use

Besifloxacin is unique among fluoroquinolones in that it was never developed for systemic use. This exclusivity to topical application may help reduce the risk of fostering systemic antibiotic resistance 12.

Dosage of Besifloxacin

Understanding the proper dosage is key to maximizing the effectiveness of besifloxacin while minimizing side effects. Treatment regimens are designed to be straightforward and patient-friendly.

Formulation	Recommended Dose	Duration	Sources
Ophthalmic 0.6% suspension	1 drop in affected eye(s) 3 times daily (every 4–12 hours)	5–7 days	1, 5, 8, 4, 13
Alternative regimen	1 drop twice daily	3 days (for select cases)	6, 7, 13
Surgical use	Perioperative dosing (varies by protocol)	Short-term	11

Table 2: Besifloxacin Dosage Recommendations

Standard Dosing for Bacterial Conjunctivitis

The FDA-approved and most widely used regimen is one drop of besifloxacin ophthalmic suspension 0.6% in the affected eye(s) three times daily (TID), spaced 4 to 12 hours apart, for 5 to 7 days 5 8 13. Clinical studies have shown this dosing achieves high rates of both clinical resolution and bacterial eradication 1 4 5.

Shorter Dosing Regimens

Recent studies have explored shorter courses with twice-daily (BID) dosing. A regimen of one drop twice daily for 3 days has demonstrated superior bacterial eradication rates compared to placebo and high clinical efficacy, making it a potential option for patients who prefer a simplified schedule 6 7 13. However, this is not yet the standard recommendation in all treatment guidelines.

Special Situations: Surgical Prophylaxis and Off-Label Use

In the context of cataract or LASIK surgery, besifloxacin is used perioperatively, with dosing protocols tailored to the surgical workflow. Its safety and tolerability in these settings have been well established 11.

Pediatric Use

Besifloxacin is approved for patients aged 1 year and older, with the same dosing protocols as adults 5 6 7 8.

Side Effects of Besifloxacin

No medication is without risk, but besifloxacin’s safety profile is notably favorable. Most side effects are mild and self-limited, with serious adverse events being exceedingly rare.

Adverse Event	Frequency	Severity	Sources
Eye pain	~1–11%	Mild to moderate	1, 4, 5, 12
Blurred vision	~2–12%	Mild, transient	1, 12, 5
Eye irritation	~1–12%	Mild to moderate	1, 5, 12
Conjunctival redness	~2%	Mild	13
Allergic reaction	Rare	Mild	11
Nonocular side effects	Very rare	Mild (e.g., dysgeusia)	8
Serious adverse events	None reported	N/A	8, 9, 11

Table 3: Common Side Effects of Besifloxacin

Ocular Side Effects

Most patients tolerate besifloxacin well. The most frequently reported side effects include:

• Eye pain, irritation, or discomfort: Usually mild and transient.
• Blurred vision: Often occurs immediately after instillation and resolves quickly.
• Conjunctival redness: Relatively uncommon but reported in some studies 13.
• Other: Allergic or hypersensitivity reactions are very rare, with isolated cases reported in surgical patients 11.

Nonocular Side Effects

Systemic absorption is minimal, with rare reports of mild taste disturbances (dysgeusia) and no serious systemic side effects documented 8.

Safety in Special Populations

• Pediatrics: Safe in children ≥1 year old, with a similar side effect profile to adults 6 7 8.
• Surgical Patients: No increase in adverse events when used perioperatively 11.
• Keratitis: Well tolerated when used off-label for corneal infections 9.

Comparison with Other Fluoroquinolones

In head-to-head trials, besifloxacin’s tolerability is comparable to that of moxifloxacin, with no significant difference in the incidence or severity of adverse events 4 11.

Interactions of Besifloxacin

Drug interactions are always a concern with antibiotics, but besifloxacin’s topical administration limits its potential for systemic interactions. However, understanding both its pharmacological and biological interactions is still important.

Interaction Type	Clinical Relevance	Notes	Sources
Systemic drug interactions	Minimal/none	Topical use only, low systemic absorption	5, 8, 13
Protein binding (experimental)	Demonstrated interaction with serum albumin in vitro	Not clinically significant for topical use	15
Other ophthalmic agents	None reported	Can be used with other eye drops if spaced appropriately	5
Resistance-related interactions	Lower risk of resistance development	Unique molecular structure, retains potency against resistant strains	14, 12

Table 4: Besifloxacin Interactions Overview

Systemic Drug Interactions

Because besifloxacin is administered topically and has negligible systemic absorption, it does not interact with other systemic medications. This is a significant advantage for patients on multiple medications or with complex medical conditions 5 8 13.

Experimental Protein Binding

Laboratory studies have shown that besifloxacin can bind to serum albumin in vitro, primarily via electrostatic interactions, leading to conformational changes in the protein 15. However, this has no known clinical impact when besifloxacin is used as an eye drop.

Use with Other Ophthalmic Agents

Besifloxacin can be safely used alongside other ophthalmic medications, but it is generally recommended to separate the administration of different eye drops by at least 5–10 minutes to ensure optimal absorption 5. No specific interactions with other topical agents have been reported.

Resistance Considerations

Unlike many older fluoroquinolones, besifloxacin retains activity against bacteria harboring common resistance mutations. Its unique chemical structure allows it to remain effective even against pathogens resistant to ciprofloxacin, levofloxacin, and similar drugs 14. This makes it an important tool in combating antibiotic resistance in ocular infections 12.

Conclusion

Besifloxacin is a modern ophthalmic antibiotic designed with patient safety, convenience, and efficacy in mind. With its broad-spectrum activity—including effectiveness against drug-resistant bacteria—and outstanding tolerability profile, it fills an important niche in the treatment of eye infections.

Key Takeaways:

• Indications: Approved for bacterial conjunctivitis; also used off-label for keratitis and surgical prophylaxis 1 4 5 9 11 12 13.
• Dosage: Standard regimen is one drop thrice daily for 5–7 days, with some evidence supporting twice-daily dosing for shorter durations 1 5 6 7 8 13.
• Side Effects: Mostly mild, transient, and ocular in nature; serious adverse events are rare or nonexistent 1 4 5 8 9 11 12 13.
• Interactions: Minimal systemic interactions due to topical use; retains activity against resistant bacteria 5 8 13 14 15.
• Pediatric and Surgical Use: Safe for children ≥1 year and for perioperative prophylaxis in eye surgeries 6 7 8 11.

Besifloxacin offers a reliable, well-tolerated option for managing bacterial eye infections in both adults and children, with the added benefit of addressing the growing challenge of antibiotic resistance in ocular pathogens. If you or your patient is prescribed besifloxacin, you can feel confident in its safety and effectiveness when used as directed.