Quinolone
Cinoxacin targets bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes essential for maintaining DNA supercoiling and topology during replication and transcription. DNA gyrase is responsible for introducing negative supercoils into bacterial DNA, while topoisomerase IV decatenates interlinked daughter chromosomes following replication. By inhibiting these enzymes, cinoxacin prevents bacterial DNA synthesis and cell division. This mechanism is characteristic of the quinolone class of antibiotics and confers bactericidal activity.

Many gram-negative aerobic bacteria are inhibited by cefoxacin (0-200μg/mL, approximately, 3-24 h), with MIC values ranging from 4 to 64 μg/mL[2].
Cinoxacin demonstrates potent antibacterial activity against a broad spectrum of Gram-negative bacteria, including E. coli and other uropathogens. It exhibits multifaceted bioactivities, showing inhibitory activity at low concentrations against enzymes such as beta-lactamase, chymotrypsin, and malate dehydrogenase (MDH), with all inhibition levels below 5.0%. The compound's primary antibacterial effect is mediated through DNA gyrase and topoisomerase IV inhibition, leading to bacterial cell death. Its activity is enhanced in the urinary tract due to favorable tissue distribution.

With ED50 values ranging from 8.1 to 58.6 mg/kg, isoxacin (oral administration, 1.7 g/kg, treated at 1 and 5 h postinfection) is effective against experimental bacterial infections in mice[2].
Cinoxacin is effective in vivo against urinary tract infections, particularly those caused by susceptible Gram-negative organisms. In animal models, it demonstrates good oral bioavailability and achieves therapeutic concentrations in the kidney and bladder. The compound is primarily used for the treatment of acute and chronic urinary tract infections. It has been shown to be effective in both human and veterinary medicine, although its use has largely been superseded by newer fluoroquinolones with broader spectra and improved pharmacokinetics.

In vitro enzyme assays for cinoxacin typically assess its inhibition of DNA gyrase and topoisomerase IV. These assays involve incubating the enzyme with a DNA substrate (usually supercoiled plasmid DNA) in the presence of varying concentrations of cinoxacin. The supercoiling or relaxation activity of the enzyme is monitored by agarose gel electrophoresis. IC50 values are determined by quantifying the extent of DNA supercoiling inhibition. Additional assays may evaluate binding affinity to the enzyme-DNA complex using surface plasmon resonance or fluorescence polarization techniques.

Cell Line: Gram-negative aerobic bacteria (Escherichia coli, Proteus sp. etc.)
Concentration: 0-200μg/mL approximately
Incubation Time: 3-24 h
Result: reduced the number of cells (by 68% to 73%) at 40 and 60 μM and inhibited basal cell proliferation (40% in FB-2 and 35% in WRO) at 10 μM.
Cell-based assays for cinoxacin involve culturing susceptible bacterial strains (e.g., E. coli) in Mueller-Hinton broth and treating them with serial dilutions of the compound. Minimum inhibitory concentrations (MICs) are determined by measuring optical density after 16-24 hours of incubation at 37°C. Time-kill kinetics assays assess the bactericidal activity over time. For mammalian cell studies, cinoxacin is tested for cytotoxicity using standard assays such as MTT or neutral red uptake in relevant cell lines (e.g., kidney epithelial cells) to evaluate tissue compatibility.

Animal Model: Indicated bacterial infected mice model[2]
Dosage: 1.7 g/kg, treated at 1 and 5 h postinfection
Administration: Oral administration
Result: demonstrated antibacterial activity, with a range of 81 to 58.6 mg/kg for the ED50 value.
In vivo animal models for cinoxacin typically involve rodent models of urinary tract infection. Mice or rats are infected with a pathogenic E. coli strain via intravesical or intravenous inoculation. Cinoxacin is administered orally or via injection at doses ranging from 5 to 50 mg/kg. Efficacy is assessed by measuring bacterial burden in urine, bladder, and kidney tissues after treatment. Pharmacodynamic parameters such as the ratio of area under the curve to MIC (AUC/MIC) are calculated to optimize dosing regimens.

Absorption, Distribution and Excretion
Absorbed rapidly after oral administration. While food intake may delay absorption, it does not affect the total amount of drug absorbed. Metabolism/Metabolites Primarily metabolized in the liver, approximately 30-40% is metabolized into inactive metabolites. Biological Half-Life The mean serum half-life is 1.5 hours, but it may exceed 10 hours in cases of renal insufficiency.
Cinoxacin is well absorbed after oral administration, achieving significant concentrations in the prostate (60% of serum) and bladder (80% of serum). The compound is primarily excreted unchanged in urine, making it particularly suitable for urinary tract infections. It has a half-life of approximately 1-2 hours in humans. Protein binding is moderate. Cinoxacin is metabolized in the liver to a limited extent, with the majority of the dose recovered in the urine within 24 hours. Its pharmacokinetic profile supports once- or twice-daily dosing for uncomplicated infections.

Protein Binding
60% to 80%
Cinoxacin is generally well tolerated but can cause gastrointestinal disturbances, nausea, and headache. As with other quinolones, there is a potential for adverse effects on the central nervous system, including dizziness and confusion. Photosensitivity reactions have been reported. Cinoxacin is contraindicated in patients with a history of quinolone hypersensitivity. In animal studies, it has shown some potential for arthropathy in juvenile animals, which is a class effect of quinolones. Long-term safety data are limited due to its obsolescence.

[1]. Cinoxacin: mechanism of action, spectrum of activity, pharmacokinetics, adverse reactions, and therapeutic indications. Pharmacotherapy. 1982 Sep-Oct;2(5):266-72.

[2]. Compound 64716, a new synthetic antibacterial agent. Antimicrob Agents Chemother. 1973 Oct;4(4):415-20.

Cinoxacin belongs to the quinolones class of compounds. Its chemical name is 6,7-methylenedioxyquinolones-4(1H)-one, with an ethyl group at the 1-position and a carboxylic acid group at the 3-position. It is an analog of oxaquinic acid and has similar antibacterial activity. Cinoxacin was previously used to treat urinary tract infections. It is both an antibacterial and anti-infective drug. It belongs to the quinolones class of compounds and is an oxocarboxylic acid and oxoheterocyclic compound.
A synthetic antibacterial drug associated with oxaquinic acid and nalidixic acid, used to treat urinary tract infections.
A synthetic antibacterial drug associated with oxaquinic acid and nalidixic acid, used to treat urinary tract infections.
Indications

For the treatment of primary and recurrent urinary tract infections in adults caused by the following susceptible microorganisms: Escherichia coli, Proteus mirabilis, Proteus vulgaris, Klebsiella spp. (including Klebsiella pneumoniae), and Enterobacter spp.
FDA Label
Mechanism of Action
Evidence suggests that sinofloxacin binds strongly but reversibly to DNA, interfering with RNA synthesis and thus protein synthesis. It also appears to inhibit DNA gyrase. This enzyme is essential for the proper separation of replicated DNA. Inhibition of this enzyme inhibits DNA replication and cell division.
Pharmacodynamics
Sinofloxacin is a synthetic antibacterial agent with in vitro antibacterial activity against a variety of Gram-negative aerobic bacteria, particularly Enterobacteriaceae strains. Sinofloxacin inhibits bacterial deoxyribonucleic acid (DNA) synthesis, exhibiting bactericidal activity and is effective across the entire urinary pH range. Cross-resistance with nalidixic acid has been demonstrated.

Cinoxacin was introduced in the 1970s and was used for the treatment of urinary tract infections. It is now largely obsolete, having been replaced by newer fluoroquinolones such as ciprofloxacin and levofloxacin, which offer broader antibacterial spectra and improved pharmacokinetics. The compound is still used in some regions for veterinary applications. Cinoxacin's mechanism of action—inhibition of DNA gyrase and topoisomerase IV—remains a validated target for antibacterial drug development. It is not approved by the FDA for current clinical use in humans.

C12H10N2O5

262.2182

262.058

C, 54.97; H, 3.84; N, 10.68; O, 30.51

28657-80-9

Cinoxacin-d5;2732985-25-8

2762

White to off-white solid powder

1.6±0.1 g/cm3

517.2±60.0 °C at 760 mmHg

210 °C

266.6±32.9 °C

0.0±1.4 mmHg at 25°C

1.709

0.35

1

7

2

19

449

0

O=C(C1=NN(CC)C2=C(C=C3C(OCO3)=C2)C1=O)O

VDUWPHTZYNWKRN-UHFFFAOYSA-N

InChI=1S/C12H10N2O5/c1-2-14-7-4-9-8(18-5-19-9)3-6(7)11(15)10(13-14)12(16)17/h3-4H,2,5H2,1H3,(H,16,17)

1-Ethyl-1,4-dihydro-4-oxo[1,3]dioxolo[4,5-g]cinnoline-3-carboxylic acid

Cinoxacin; Cinobac; Compound 64716; Cinoxacine; Cinoxacino; Cinoxacinum;Acid, Azolinic; Azolinic Acid;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~8.33 mg/mL (~31.77 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)