Quinolone antibiotics

Quinolone Antibiotics: Are They Safe and Effective?

What are Quinolone Antibiotics?

Quinolones are synthetic bactericidal antibiotics that can affect a wide range of gram-positive and gram-negative bacteria. The medicines are used in veterinary and human. These medications are approved by the FDA for the treatment of bronchitis, sinusitis, and some urinary tract infections only if other less toxic medicines are useless. However, in severe acute cases of bacterial prostatitis or pyelonephritis, quinolone antibiotics are recommended as first-line therapy. Most of quinolone antibiotics are fluoroquinolones that have a chemical structure with a fluorine atom, which is effective against different bacteria, including gram-negative and gram-positive.

Fluorine is the lightest halogen. At usual conditions, it exists as a highly toxic yellow gas, which is extremely reactive. Since fluoroquinolones are able to access cells easily through porins, they are often used for the treatment of various pathogens, including Mycoplasma pneumoniae, Legionella pneumophila, and others.

Quinolones are able to convert their targets, topoisomerase IV, and gyrase into toxic enzymes to fragment the chromosome of bacteria.

The following medications belong to quinolone antibiotics:

  • Lomefloxacin (Maxaquin);
  • Ofloxacin (Floxin);
  • Norfloxacin (Noroxin);
  • Ciprofloxacin (Cipro I.V., Proquin XR, and Cipro XR);
  • Moxifloxacin (Avelox and Avelox I.V.);
  • Gemifloxacin (Factive);
  • Cinoxacin (Cinobac);
  • Nalidixic acid (NegGram);
  • Trovafloxacin (Trovan);
  • Sparfloxacin (Zagam).

Historical Background

The quinolone group of antibiotics was discovered in the 1960s, which caused a significant interest right away. Nalidixic acid was the first quinolone, and today many derivatives exist on the market. Antibacterial efficacy has been enhanced thanks to changes applied to the basic molecule, for instance, at position 6, hydrogen was replaced with fluorine.

Some of the structural changes have been considered to be the cause of certain adverse events, although they have shown a significant improvement in potency and breadth of pharmacokinetics. The improved anti-Gram-positive activity is one of the most valuable achievements. Such new medications as Garenoxacin and Moxifloxacin are considered to be very perspective in the treatment of various diseases, in particular, respiratory infections.

Are Quinolones Really Safe in Use?

The modern quinolone antibiotics are believed to be safe and to have a low risk of side effects. This has been concluded from a range of studies conducted on the subject. But still, the use of these medications causes a range of doubts and questions because it is hard not to pay attention to a range of side effects caused during the use of quinolone antibiotics.

There were cases of severe side effects, and even death cases occurred during to the use of certain quinolones, but the relation between these cases and the drugs has not been confirmed.

The following are quinolone antibiotics that were found too dangerous in use so that they were removed from the market:

  • Clinafloxacin;
  • Cinoxacin;
  • Grepafloxacin;
  • Fleroxacin;
  • Trovafloxacin;
  • Flumequine;
  • Temafloxacin (Omniflox);
  • Enrofloxacin;
  • Gatifloxacin;
  • Nalidixic acid;
  • Pefloxacin;
  • Sparfloxacin, and others.

Also, the FDA regularly publishes new safety warnings regarding the use of quinolone antibiotics. They recommend considering all potential risks and effects before using these medications.

The Use of Quinolone Antibiotics in Children

Fluoroquinolones can be used in children only under certain circumstances. For instance, in the UK, the use of quinolone antibiotics by children is strictly restricted. A range of studies was conducted in order to determine the safety of quinolone antibiotics if compared to other similar treatments. There have been various adverse effects experienced, but they were considered to be unrelated to the use of the drugs.

According to meta-analyses, fluoroquinolones have little or no risk to children compared to other groups of antibiotic. The use of quinolone antibiotics may be recommended in case of the infection caused by highly antibiotic resistant bacteria, or if oral therapy or parenteral administration is preferred.

At the same time, this group of drugs has a “dark” history, and that is why they are not recommended for the use in children under 18 years old unless it is extremely necessary.

Quinolone Antibiotics Resistance

Quinolones are the commonly used class of antibiotics in the world that are able to treat a wide range of various bacterial infections, and that is why they have been prescribed quite often, which naturally led to the occurrence of quinolone-resistant bacteria. The process started in the 1990s, and today a pretty large number of such bacteria exist in the world. Quinolones resistance is a cause of mutations in topoisomerase IV and gyrase, which does not allow quinolones and enzymes to interact properly.

Over a few decades, quinolones have become important medications for the treatment of various infections, such as urinary tract infections. These antibiotics are widely used to fight many infections, including those caused by gram-positive and gram-negative bacteria, but the resistance quinolones may eliminate the ability of these medications to work properly. It is important to develop new quality quinolone drugs and to do actions needed for preventing the development of the resistance.

Side Effects

Quinolones can cause a range of side effects, including the following most common ones:

  • Nausea;
  • Dyspepsia;
  • Vomiting;
  • Dizziness;
  • Insomnia;

Despite the positive results of several studies, quinolones are associated with severe side effects affecting muscles, joints, tendons, nerves, and CNS.

Drug Interaction

The quinolone antibiotics can interact with a range of other medications. The absorption of the drugs is reduced if they are used along with antacids that have magnesium, aluminum, or calcium. The adsorption of the drugs can also be reduced by iron salts, sucralfate, and zinc salts.

A range of new quinolone medications (such as enoxacin, ciprofloxacin, and pefloxacin) have the cytochrome P450 system, which may increase concentrations of theophylline to toxic levels.

Quinolones should not be used along with GABA receptors because this can cause a range of serious CNS side effects. NSAIDs should also be avoided if quinolone antibiotics are taken.