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The quinolones are a family of broad-spectrum antibiotics. The parent of the group is nalidixic acid. The majority of quinolones in clinical use belong to the subset of fluoroquinolones, which have a fluoro group attached the the central ring system.

Mechanism

Quinolones act by inhibiting the bacterial DNA gyrase and/or the topoisomerase II enzyme. This way they inhibit DNA replication and transcription. Quinolones, and fluroquinolones alike, are bactericidal drugs, actively killing bacteria. Quinolones can enter cells easily and therefore are often used to treat intracellular pathogens such as Legionella pneumophila and Bacillus anthracis.

Adverse effects

At one time the quinolone antibiotics were considered relatively safe. With increasing experience however a variety of side effects have become evident. For example, numerous case reports (since 1965) have implicated their use in cases of spontaneous tendon ruptures and tendon damage, especially with the concurrent use of a systemic corticosteroid. In the fall of 2004 the Food and Drug Administration upgraded the warnings found within the package inserts for all drugs within this class regarding such serious adverse reactions. These new warnings included:

Peripheral neuropathy (irreversible nerve damage): "rare cases of sensory or sensor motor axonal polyneuropathy affecting small and or large axons resulting in paresthesias, hypoaesthesias, dysesthesias, and weakness have been reported in patients taking quinolones. Therapy should be discontinued if the patient experiences symptoms of neuropathy including pain, burning, tingling, numbness and or weakness or is found to have deficits in light touch, pain, temperature, position sense, vibratory sensation, and or motor strength in order to prevent the development of an irreversible condition."

Tendon damage: "Ruptures of the shoulder, hand, Achilles tendon or other tendons that require surgical repair or resulted in prolonged disability have been reported in patients receiving quinolones. Post-marketing surveillance reports indicate that this risk may be increased in patients receiving concomitant corticosteroids, especially the elderly. Fluoroquinolone therapy should be discontinued if the patient experiences pain, inflammation, or rupture of a tendon. Patients should rest and refrain from exercise until diagnosis of tendonitis or tendon rupture had been excluded. Tendon rupture can occur during or after therapy with quinolones."

As well as the following:

Resistance

Resistance to quinolones can develop rapidly, even during a course of treatment. Numerous pathogens, including Staphylococcus aureus, enterococci and Streptococcus pyogenes now exhibit resistance worldwide.M Jacobs, Worldwide Overview of Antimicrobial Resistance. International Symposium on Antimicrobial Agents and Resistance 2005. Widespread veterinary usage of quinolones in Europe has been implicated. Because of this serious problem the quinolones are generally not considered a first line agent but rather a drug of resort when therapy with other classes of antibiotics has failed or is inappropriate. It is hoped that judicious use of quinolone drugs may prolong the useful life of this group.

Jim Hoover, regional manager for state government affairs for the Bayer Corporation for the five northwest States, discussed the second and third generation quinolones. He states that "...Normally the quinolone class of drugs is used in patients who have failed at least one prior therapy. The patients tend to be fairly ill and require relatively acute care that often may be the last step before they are admitted into the hospital. …By the time the physicians get to this classification, they tend to have a good idea of what bacteria is involved, what antibiotic is the most potent for the bacteria and which penetrates that particular body side the best. …These drugs are often the last step before admission into the hospital..."Jim Hoover, Alaska Pharmacy and Therapeutics Committee March 19, 2004

Generations

The quinolones are divided into generations based on their antibacterial spectrum. The earlier generation agents are generally more narrow spectrum than the later ones.

1st generation

2nd generation

3rd generation

4th generation

In development

Veterinary use

The quinolones have been widely used in agriculture and several agents exist which have veterinary but not human use.

--Ananyo u 08:59, 18 July 2006 (UTC)Dr. Ananya bhar

External links

Fluoroquinolone antibiotics

Fluorchinolone | Quinolona | Quinolone | Fluoroquinolone norfloxacin in combination with tinidazole or metronidazole is frequently used in veterinary medicine, specially in mixed enteric infection with bacteria and protozoa. the generic names are Normet susupension(norfloxacin with metronidazole), TiniNF suspension(tinidazole with norfloxacin)etc. Quinoloner | Chinolony | Quinolona | Chinolón

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Quinolone".

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