Besifloxacin Hydrochloride

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Cat Number

API405165619

CAS Number

405165-61-9

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Product Detail Description Scientific Support Customer Q&A

CAS Number

405165-61-9

EINECS

696-612-6

Storage

Store at room temperature

Synonyms

Besifloxacin HCl; SS734; 7506A6J57T; DTXSID20193529

Molecular Formula

C19H22Cl2FN3O3

Molecular Weight

430.3

Smiles

C1CCN(C[C@@H](C1)N)C2=C(C=C3C(=C2Cl)N(C=C(C3=O)C(=O)O)C4CC4)F.Cl

Appearance

Pale yellow solid

Melting Point

>210°C (dec.)

Boiling Point

607.0±55.0°C at 760 mmHg

Relative Density

1.5±0.1

General Description

Besifloxacin hydrochloride is a fluoroquinolone antibiotic with an 8‑chloro substituent and an N‑cyclopropyl group, distinguishing it from other quinolones. The hydrochloride salt provides water solubility. The molecule has a tricyclic pyridobenzoxazine core, which enhances its binding to DNA gyrase and topoisomerase IV. Besifloxacin is the most potent fluoroquinolone against methicillin‑resistant Staphylococcus aureus (MRSA).

Mechanism of Action

Besifloxacin inhibits both bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes essential for DNA replication, transcription, and repair. Unlike many fluoroquinolones, it has balanced activity against both targets, reducing the likelihood of resistance emergence. The 8‑chloro group improves activity against anaerobic organisms and enhances the post‑antibiotic effect.

Application

Besifloxacin is indicated for the treatment of bacterial conjunctivitis caused by susceptible organisms, including Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. It is a topical ophthalmic agent with no systemic absorption concerns. The balanced dual‑target inhibition provides activity against fluoroquinolone‑resistant strains that have mutations in one of the target enzymes.

In a multicenter randomized double‑masked study (33 neonates ≤31 days old with bacterial conjunctivitis), topical besifloxacin 0.6% or gatifloxacin 0.3% three times daily for 7 days were compared. Clinical resolution at day 8‑9 was 75.0% vs. 70.6% (ITT) and 84.6% vs. 77.8% (mITT). Bacterial eradication rates were 92.3% vs. 88.9% (mITT). No adverse events were reported in the besifloxacin group; gatifloxacin AEs were not treatment‑related. Both agents appeared effective and safe, though larger studies are needed.

Fig. 1 Bacterial eradication rates at visits 3 and 5 (culture-positive, baseline-designated study eyes, modified intent-to-treat population, last observation carried forward). (Sanfilippo CM, et al., 2017)

References

Sanfilippo CM, et al. Besifloxacin Ophthalmic Suspension 0.6% Compared with Gatifloxacin Ophthalmic Solution 0.3% for the Treatment of Bacterial Conjunctivitis in Neonates. Drugs R D. 2017;17(1):167-175.

Does Besifloxacin Hydrochloride require protection from light during storage?

Yes, it is photosensitive. UV light can cause photodegradation of the quinolone core. Store in light-resistant containers, preferably original opaque packaging.

What is the recommended storage temperature for Besifloxacin Hydrochloride?

Store at controlled room temperature (15-25°C). Avoid temperatures above 30°C, which can accelerate decarboxylation and formation of the desfluoro impurity.

Is Besifloxacin Hydrochloride stable in ophthalmic suspension formulations?

Yes, when formulated with preservatives and protected from light.

How is the impurity besifloxacin ethylenediamine analog (a process-related impurity) monitored?

This impurity is quantified using a stability-indicating HPLC method, ensuring it remains within ICH qualification thresholds.