Fluoroquinolones: Classification and Therapeutic Uses

Fluoroquinolones are antibiotics that act by inhibiting DNA gyrase and inhibition of DNA type IV topoisomerase. Specific drug is intended for specific conditions. Before taking any of the quinolones, advice of a highly qualified health professional is needed. These medicines can cure certain bacterial infections but can also produce side effects and adverse effects. Proper use is recommended to avoid unwanted effects.

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.

• Nalidixic acid

*Reported side effects with this drug are cranial nerve palsy, metabolic acidosis and toxic psychosis.

• Cinoxacin

	United States	United Kingdom	Philippines
Generic name	Brand Names
Nalidixic Acid	NegGram	Uriben
Cinoxacin	Cinoxacin Cinobac	Uriben

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.

• Lomefloxacin
• Enoxacin
• Norfloxacin

*Patients should definitely avoid driving or skilled activities when          taking Norfloxacin as it prejudice performance with the said tasks.   400 mg of this drug should be given twice a day for 7 – 10 days. If      in case the urinary tract infection is uncomplicated, Norfloxacin is    given for 3 days only. Chronic relapsing of UTI may occur; in this case 400mg twice daily of Norfloxacin is given up to 12 weeks. If     suppression of the infection is acceptable then the dosage may reduce to 400 mg once a day for 4 weeks.

	United States	United Kingdom	Philippines
Generic Names	Brand Names
Lomefloxacin	Maxaquin
Enoxacin	Penetrex
Norfloxacin	Noroxin	Norfloxacin (non-proprietary) Utinor	Euroflox Fasqilon Jaydisyn Norex Urithracin Utiflox Winaflox

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.

• Ciprofloxacin

*Effects of Ciprofloxacin are enhanced by alcohol.

• Ofloxacin

	United States	United Kingdom	Philippines
Generic Names	Brand Names
Ciprofloxacin	Cipro	Ciprofloxacin (Non-proprietary) Ciproxin	Ciloxan Ciprobay Cipromax Cipromet Qinoflox Xipro
Ofloxacin	Floxin	Ofloxacin (Non-proprietary) Tarivid	Inoflox Imoflox Qinolon

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.

• Moxifloxacin
• Levofloxacin

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. 

• Sparfloxacin
• Gatifloxacin

*Gatifloxacin was withdrawn due to increased frequency of hypoglycaemia and hyperglycemia.

	United States	United Kingdom	Philippines
Generic Names	Brand Names
Moxifloxacin	Avelox	Avelox	Avelox Vigamox
Levofloxacin	Levaquin	Tavanic	Levox Levocin Pravox Wilovex
Sparfloxacin	Zagam
Gatifloxacin (Withdrawn)	Tequin

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.

• Trovafloxacin

        *Trovafloxacin was withdrawn due to the risk of hepatic toxicity.

	United States		United Kingdom	Philippines
Generic Names		Brand Names
Trovafloxacin (Withdrawn)	Trovan

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. 

References:

Merck Manuals

British National Formulary 56

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