Active Ingredients

Quinolones – Effect, Application & Risks


Quinolones represent a separate class of antibiotics . They all have the same basic chemical structure, which is derived from quinoline. A large number of different quinolones can be prepared by exchanging the substituents on the nitrogen-containing ring system.

What are quinolones?

The basic structure of quinolones is a nitrogen-containing ring system derived from quinoline. The ring system is composed of a benzene ring and a pyridine ring. In the quinolones there is also a carboxylic acid and a carbonyl group on the nitrogen-containing pyridine ring. Different substituents are attached to the benzene ring and to the nitrogen atom of the pyridine ring.

Basically, the quinolones work by inhibiting the bacterial enzyme gyrase. The fluoroquinolones also inhibit bacterial growth via another biochemical pathway, which has not yet been fully elucidated. Because of the extended action of fluoroquinolones, they have a wide range of uses against many species of bacteria .

The starting substance for the synthesis of the quinolones is the active ingredient nalidixic acid, which is no longer used. Nalidixic acid, in turn, is also produced synthetically. Alternatively, the non-fluorous quinolones have a piperazine ring at the appropriate position.

The spectrum of activity of the quinolones is very broad. There are both limited-acting and broad-spectrum and intensive-acting representatives of this class of active ingredients. The basic mechanism of antibacterial action is the same for all quinolones. Only the substituents determine the intensity and selectivity of their influence.

Pharmacological action

The antibacterial effect of the quinolones is based on the inhibition of bacterial gyrase. Gyrase is an enzyme found only in bacteria. It decoils and restores the coiled structure of DNA. The genetic code of the bacterial DNA can only be read and translated into proteins in the uncoiled state .If the gyrase is blocked, however, the process of untwisting the DNA is no longer active. The DNA can no longer be read properly, with the result that bacterial growth is inhibited. Existing bacteria then slowly die off. With the fluoroquinolones there is an additional mechanism that leads to the inhibition of growth of many bacterial strains. However, this process has not yet been fully elucidated.

The substituents determine the strength of the effect and at the same time which bacteria are combated. Some quinolones are primarily effective against gram-positive bacteria, others against gram-negative bacteria. In addition to quinolones, which have a broad spectrum of activity against many types of bacteria, there are also quinolones with a very limited spectrum of activity. Since the gyrase is only found in bacteria, the quinolones can only treat bacterial infections . They have no effect against fungi and viruses .

Medical Application & Use

Quinolones are used to fight bacterial infections. In order to be able to determine which antibiotics of this class of active ingredients promise the best chance of healing, the type of bacteria must first be determined. Because not every quinolone is effective against every bacterium. This fact results in the different areas of application.

The medication can be administered in various ways. They can be taken orally as tablets, capsules or in the form of juices or injected as an infusion solution . All quinolones are effective for urinary tract and kidney infections . The drugs norfloxacin or pipemidic acid can be used for urinary tract infections. Norfloxacin is also effective against the sexually transmitted disease gonorrhea (clap). Drugs such as enoxacin can also be used for respiratory , lung or skin infections.

The drug levofloxacin has an even wider range of applications . In addition to urinary tract and respiratory tract infections, it can also be used for skin, soft tissue and eye infections . The two drugs ofloxacin and ciprofloxacin cover the widest range of applications . In addition to kidney, urinary tract, respiratory tract or skin infections, the applications also include bone and joint infections, infections of the digestive tract , the gallbladder , the ear, nose and throat area and the eyes. In addition, ciprofloxacin can also be used in sepsis ( blood poisoning), anthrax or cystic fibrosis ( mucoviscidosis ) in children.

Fluoroquinolones are very well absorbed by the body’s tissues , so that they can quickly be found everywhere in the organism. Therefore, fluoroquinolones can also fight infections that are difficult to reach with other drugs, such as bone or prostate infections .

Risks & side effects

Quinolones interact with other drugs, either reducing their effectiveness or causing side effects . So, the effectiveness of quinolones is reduced by divalent calcium or magnesium salts, as well as by antacids, since together they form complexes.When used with antirheumatic agents and steroids , states of excitement can occur. Furthermore, the use of the medication can lead to various side effects. Nausea and vomiting are observed . Diarrhea and abdominal pain are less common.

Neurological disorders such as increased excitability, restlessness, insomnia , dizziness or even hallucinations can occur in rare cases.

There is increased sensitivity to solar radiation during treatment with quinolones. Sunbathing or sunlamps are contraindicated during quinolone therapy. Studies also indicate that quinolones have cartilage -damaging properties. Cardiac arrhythmias are also possible due to disturbances in the conduction of excitation .

Very rare side effects are changes in the blood count and allergic reactions . No quinolones should be administered during pregnancy and breastfeeding . The same applies to use in children and adolescents. A contraindication is also present in cerebral spasms , severe renal insufficiency or cardiac arrhythmia.

Website | + posts

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.