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Quinolones – Types, Side Effects, Interactions

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 6 min read

Quinolone antibiotic is any member of a large group of broad-spectrum bactericides that share a bicyclic core structure related to the compound 4-quinolone. They are used in human and veterinary medicine to treat bacterial infections, as well as in animal husbandry. Nearly all quinolone antibiotics in modern use are fluoroquinolones, which contain a fluorine atom in their chemical structure and are effective against both Gram-negative and Gram-positive bacteria. One example is ciprofloxacin, one of the most widely used antibiotics worldwide.

Types of Quinolone

First-generation

  • flumequine
  • oxolinic acid
  • rosoxacin

Structurally related first-generation drugs, but formally not 4-quinolones, include cinoxacin, nalidixic acid, and piromidic acid, pipemidic acid

Second generation

The second-generation class is sometimes subdivided into “Class 1” and “Class 2”.

  • ciprofloxacin 
  • fleroxacin
  • lomefloxacin 
  • nadifloxacin
  • norfloxacin
  • ofloxacin 
  • pefloxacin
  • rufloxacin

A structurally related second-generation drug, but formally not a 4-quinolone, is enoxacin

Third generation

Unlike the first and second generations, the third generation is active against streptococci.

  • balofloxacin
  • grepafloxacin
  • levofloxacin 
  • pazufloxacin
  • sparfloxacin 
  • temafloxacin

A structurally related third-generation drug, but formally not a 4-quinolone, is tosufloxacin

Fourth generation

Fourth-generation fluoroquinolones act at DNA gyrase and topoisomerase IV. This dual action slows development of resistance.

  • clinafloxacin
  • gatifloxacin 
  • moxifloxacin
  • sitafloxacin
  • prulifloxacin
  • besifloxacin

Two structurally related third generation drugs, but formally not 4-quinolones, are gemifloxacin  and trovafloxacin

Types  of Quinolone

1st generation

  • Cinoxacin
  • Flumequine
  • Nalidixic acid
  • Oxolinic acid
  • Pipemidic acid
  • Piromidic acid
  • Rosoxacin

2nd generation

  • Ciprofloxacin
  • Ofloxacin
  • Enoxacin
  • Fleroxacin
  • Lomefloxacin
  • Nadifloxacin
  • Norfloxacin
  • Pefloxacin
  • Rufloxacin

3rd generation

  • Levofloxacin
  • Balofloxacin
  • Grepafloxacin
  • Pazufloxacin
  • Sparfloxacin
  • Temafloxacin
  • Tosufloxacin

4th generation

  • Besifloxacin
  • Delafloxacin
  • Gatifloxacin
  • Finafloxacin
  • Gemifloxacin
  • Moxifloxacin
  • Clinafloxacin
  • Garenoxacin
  • Prulifloxacin
  • Sitafloxacin
  • Trovafloxacin/Alatrofloxacin

Vet.

  • Danofloxacin
  • Difloxacin
  • Enrofloxacin
  • Ibafloxacin
  • Marbofloxacin
  • Orbifloxacin
  • Pradofloxacin
  • Sarafloxacin

Mechanism of Action of Quinolone

The bactericidal action of ciprofloxacin results from inhibition of the enzymes topoisomerase II (DNA gyrase) and topoisomerase IV, which are required for bacterial DNA replication, transcription, repair, strand supercoiling repair, and recombination.
The mechanism by which ciprofloxacin’s inhibition of DNA gyrase or topoisomerase IV results in death in susceptible organisms has not been fully determined. Unlike beta-lactam anti-infectives, which are most active against susceptible bacteria when they are in the logarithmic phase of growth, studies using Escherichia coli and Pseudomonas aeruginosa indicate that ciprofloxacin can be bactericidal during both logarithmic and stationary phases of growth; this effect does not appear to occur with gram-positive bacteria (e.g., Staphylococcus aureus). In vitro studies indicate that ciprofloxacin concentrations that approximate the minimum inhibitory concentration (MIC) of the drug induce filamentation in susceptible organisms; high concentrations of the drug result in enlarged or elongated cells that may not be extensively filamented. Although the bactericidal effect of some fluoroquinolones (e.g., norfloxacin) evidently requires competent RNA and protein synthesis in the bacterial cell, and concurrent use of anti-infectives that affect protein synthesis (e.g., chloramphenicol, tetracyclines) or RNA synthesis (e.g., rifampin) inhibit the in vitro bactericidal activity of these drugs, the bactericidal effect of ciprofloxacin is only partially reduced in the presence of these anti-infectives. This suggests that ciprofloxacin has an additional mechanism of action that is independent of RNA and protein synthesis.

Indications of Quinolone

  • Upper/Lower respiratory tract infection  (respiratory, skin, soft tissue, UTI, ENT)
  • Infectious diarrheas caused by E. coli, Campylobacter jejuni, and Shigella bacteria.
  • Skin infections
  • Lung or airway Infections, for example, TB (tuberculosis), pneumonic and septicemic plague due to Yersinia pestis (Y. pestis), lower respiratory tract infections, and chronic bronchitis)
  • Bone and Joint Infections
  • Anthrax patients with fever and low white blood cell counts, and intra-abdominal infections.
  • Acute bacterial otitis media
  • Skin and skin structure infections
  • Urinary tract infections
  • Uncomplicated gonorrhea
  • Pelvic inflammatory disease
  • Bacterial septicemia
  • Intra-abdominal infections
  • Pelvic Inflammatory Disease
  • Meningitis
  • Osteomyelitis
  • Pelvic Inflammatory Disease
  • Surgical prophylaxis
  • Community-acquired pneumonia
  • Acute otitis media
  • Intra-abdominal infections
  • Complicated urinary tract infections (including pyelonephritis)
  • Infections of bones and joints
  • Complicated skin and soft tissue infections
  • Gonorrhea
  • Syphilis
  • Bacterial Endocarditis.
  • Meningococcal Meningitis Prophylaxis
  • Salmonella Enteric Fever
  • Salmonella Gastroenteritis
  • Community-acquired pneumonia
  • Hospital-acquired pneumonia
  • Acute otitis media
  • Intra-abdominal infections
  • Complicated urinary tract infections (including pyelonephritis)
  • Infections of bones and joints
  • Complicated skin and soft tissue infections
  • For treatment of acute exacerbations of chronic obstructive pulmonary disease in adults
  • For treatment of disseminated Lyme borreliosis (early (stage II) and late (stage III)) in adults and children including neonates from 15 days of age.
    |For Pre-operative prophylaxis of surgical site infections

Side Effects of Quinolone

Most common

More common

Rare

Drug Interactions of Quinolone

Fluoroquinolones may interact with following drugs, supplements, & may change the efficacy of drugs

References

Quinolones – Types, Side Effects, Interactions

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

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Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.