Fluoroquinolones toxicity

What are the fluoroquinolones?

Fluoroquinolones is a large group of broad-spectrum antibiotics including ciprofloxacin, gemifloxacin, levofloxacin and gatifloxacin that block the bacterial DNA synthesis by inhibiting the bacterial enzymes such as DNA gyrase and topoisomerase IV. These drugs are active against both Gram-positive and Gram-negative bacteria, therefore, had been extensively used for the treatment of various bacterial infections until recently when more and more data regarding fluoroquinolones toxicity has been reported. Namely, fluoroquionolones were accused of neurotoxicity, cardiotoxicity and musculoskeletal abnormalities leading to the FDA (the U.S. Food and Drug Administration) recommendation to avoid administration of these medications unless it’s vital. Despite the fact that these adverse events are considered rare their disabling potency is high. Some of these antibiotics were forbidden due to their toxicity including gatifloxacin (though eye drops are still available), gemifloxacin and trovafloxacin.

Red and white capsules pill spilled out from white plastic bottle container. Antibiotics drug resistance. Antimicrobial capsule pills. Pharmaceutical industry. Pharmacy. Indications for fluoroquinolones administration

So when are the fluoroquinolones essential enough to use them despite their adverse effects?

  • Urinary tract infections are susceptible to fluoroquinolones. These antibiotics also proved to be effective for the treatment of diarrhea caused by bacteria.
  • Ciprofloxacin is indicated for the treatment and prevention of anthrax. 
  • Ciprofloxacin and levofloxacin are occasionally prescribed for tuberculosis.
  • Severe pneumonia may also require administration of fluoroquinolones.

Adverse effects

Gastrointestinal adverse effects

These side effects are the most common and include mild abdominal discomfort, nausea, vomiting, and loss of appetite. Sometimes diarrhea (watery stool) may occur.

Neurologic adverse effects

Neurologic side effects develop quite frequently. Headache, dizziness, sleep disturbances, and mood swings were reported in up to 10-11% of individuals taking fluoroquinolones. In rare cases, patients may experience hallucinations and seizures. These antibiotics are also associated with a risk of peripheral neuropathy, peripheral nerve damage which causes a tingling, numbing or burning sensation and senses alterations in the limbs. Fluoroquinolones are known to block the activity of the neuromuscular synapses so the muscles don’t get the stimulus from the nervous system and muscular weakness becomes a problem. Therefore, fluoroquinolones administration should be avoided in individuals who suffer from myasthenia gravis (chronic autoimmune disease characterized by weakness of the skeletal muscles) as it may exacerbate the disease. 

Cardiac adverse effects

Fluoroquinolones administration is associated with QT prolongation and, therefore, increased risk of developing cardiac arrhythmia.

Musculoskeletal adverse effects

Even a short term use of fluoroquinolones is associated with an increased risk of developing tendinopathy followed by a rupture of the Achilles tendon though other tendons may also be affected (shoulder, hand, thumb). Individuals over 60 years old and those who take corticosteroids are especially at risk of developing this adverse effect. Recently FDA has recommended stopping the administration of fluoroquinolones if there is any pain, swelling or signs of inflammation of the tendon. Usually tendinopathy develops after day 8 of the drug usage.

Liver dysfunction

Some fluoroquinolones such as gatifloxacin, levofloxacin, and moxifloxacin are associated with an increased risk of acute liver injury developing within 1 to 39 days after the treatment initiation.

Mental health issues

There are some reports that the administration of fluoroquinolones may cause some attention disturbances, nervousness and memory impairment.

Allergic reactions and rash

The allergic reaction may occur due to any drug administration so these reactions are not specific for fluoroquinolones.

The use of Gemifloxacin is associated with the occurrence of rash.

Other adverse effects that are relatively uncommon include low white blood cell count, blood glucose levels swings (especially in individuals with diabetes mellitus), anemia, and photosensitivity. The fluoroquinolones may cause kidney damage, though it happens extremely rare.

Long-term fluoroquinolone-associated disability

It is considered that fluoroquinolones may have long-term effects on a person’s health, related to oxidative stress caused by these drugs that ruins the mitochondrial DNA. Respectively, some side effects may develop long after the treatment was ceased with even disabling consequences.

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