Fluoroquinolones are bactericidal agents for growing bacteria. It is related to nalidixic acid. The mechanism of action of this popular class of antibiotics is by inhibiting DNA gyrase and inhibition of DNA type IV topoisomerase. They basically interfere with DNA replication. These agents are highly active against Enterobacteriaceae, Pseudomonas aeruginosa, Salmonella bacteremia, Shigella, Neisseria, Haemophilus influenzae, Chlamydia, Mycobacterium tuberculosis, Chlamydophila, Moraxella catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila and Campylobacter.

These fluoroquinolones are classified by generation based on their antimicrobial activities. Brand names of these agents may vary depending on country.

First-generation agents are not often used today. They are indicated for uncomplicated lower urinary tract infections given through oral administration for 7 days. They have restrained gram-negative reactions and inconsequential systemic distribution. Patients suffering from liver disease should take these medicines with precaution.

Second-generation agents are very active in treating diseases caused by aerobic gram-negative bacilli but have narrow gram-positive activity.

Class I

Class I agents of this generation are indicated for urinary tract infections.

Class II

Class II agents are used to target infections such as complicated urinary tract infections, Nosocomial infections, Gastroenteritis, Prostatitis, and sexually transmitted diseases. Class I of these agents are given orally while Class II can be given orally or intravenously.

Third-generation agents have a wider gram-negative and atypical intracellular activity. They also have enhanced reaction against gram-positive spectrum. They gave a higher serum concentration making it more effective against bacteria like Enterobacteriaceae, Streptococci and other atypical pathogens. They have similar indication as the Class II of second generation antibiotics except that they can be given to hospitalized or non-hospitalized patients with community-acquired pneumonia. These can also be given in patients suffering from exacerbated chronic bronchitis in which patients are not responding to other antibacterial agents. These agents are administered orally and intravenously.

Some side effects that can be seen with the use of Levofloxacin are hypoglycaemia, flatulence, constipation, sometimes tachycardia and very rarely pneumonitis. This medication reacts adequately in acute sinusitis with 500 mg daily oral dose for 10-14 days. For some complicated UTI, 250 mg daily by intravenous infusion is given and may be increased in severe infections. 

Fourth-generation antibiotic inhibits both DNA gyrase and topoisomerase which enables the slowing down of resistance development. It is consider in treating intra-abdominal infections. This antibiotic can be provided through oral and intravenous administration.

There are some precautions to watch out in using quinolones. Among the occasional adverse effects that may arise are headache, dizziness, insomnia, diarrhea, nausea, dyspepsia, hypoglycaemia, tendonitis, photosensitivity and effects on central nervous system. In some cases, rashes, hallucinations, tremor, leukopenia, and urticarial may occur to patients taking these antibiotics. Quinolones are contraindicated in patients with a history of tendon disorders related to quinolone use.  Drug dosage forms of antibiotics may differ considering the site of infection and the age of the patient to take the medication.