The Truth About Fluoroquinolone Antibiotics

If you’ve ever had a bacterial infection, then you may be familiar with a group of antibiotics called fluoroquinolones, also called quinolones. In recent years, these antibiotics have been under fire for the numerous reports of severe and sometimes permanent side effects, referred to as fluoroquinolone toxicity. Continue reading to understand the potential risks and side effects of fluoroquinolones, as well as safe usage and alternative treatments. 

What Are Fluoroquinolones?

Fluoroquinolones are broad-spectrum antibiotics, which means they're used to treat a wide variety of bacterial infections. Some brand names of fluoroquinolone antibiotics that you might have heard of from television ads or from your doctor or pharmacy include Cipro (ciprofloxacin) and Levaquin (levofloxacin). 

These and other fluoroquinolones have treated numerous infections successfully, returning patients to health without any problems. However, like most human medicines, they carry some risks, one of which is fluoroquinolone toxicity.

What Do Fluoroquinolones Do To The Body?

Mechanism of Action

Fluoroquinolones are broad-spectrum antibiotics that are active against a wide range of Gram-positive and Gram-negative bacteria. These antibiotics kill bacteria by blocking enzymes required for bacterial RNA synthesis and mitochondrial DNA replication. 

Some of the bacteria against which fluoroquinolones are effective include: 

• Staphylococcus species

• Streptococcus pneumoniae 

• Streptococcus viridans

• Enterococcus faecalis

• Listeria monocytogenes

• Nocardia species

• Neisseria meningitides

• Neisseria gonorrhoeae

• Haemophilus influenzae

• Enterobacteriaceae species

• Pseudomonas aeruginosa

• Vibrio species

Note: Antibiotics, including fluoroquinolones, should never be used to treat non-bacterial infections. Antibiotic therapy is not effective against fungal and viral infections and can increase the risk of serious side effects, for example, tendon injury related to fluoroquinolones in addition to increasing the risk of antimicrobial resistance. Learn more about what happens if you take antibiotics without an infection.

Potential Risks

Inhaled, injected, and oral fluoroquinolones have been linked to serious adverse reactions, including disabling, long-lasting, and potentially irreversible adverse reactions. These serious adverse reactions can affect multiple body systems, including the musculoskeletal system and central nervous system.

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What Are The Most Serious Adverse Effects of a Patient Taking a Fluoroquinolone?

Serious Adverse Reactions

Some of the most serious adverse effects in patients taking a fluoroquinolone antibiotic include:

• Tendinopathies (problems with tendons)

• Muscle problems

• Nerves problems

• Joint pain and swelling

• Mental health problems, including memory difficulties

• Psychiatric problems such as anxiety and depression

Healthcare providers recommend stopping treatment with fluoroquinolones and seeking immediate medical evaluation if these adverse reactions occur.

Note: Ciprofloxacin-induced toxicity is the most commonly reported, but this may be because this antibiotic is the most commonly prescribed fluoroquinolone.

Symptoms of Fluoroquinolone Associated Disability (FQAD)

Some of the symptoms of fluoroquinolone-associated disability (FQAD) and serious adverse reactions are listed below:

• Tendon pain and swelling.

• Joint pain and swelling.

• Muscle weakness.

• Paresthesia (abnormal sensations like numbness, tingling, pins and needles, prickling, burning).

• Changes in vision, taste, hearing, or smell.

• Anxiety or depression.

• Problems with memory.

• Severe tiredness.

• Sleep difficulties.

Call your doctor immediately or seek emergency medical care if you develop these disabling and potentially irreversible symptoms of fluoroquinolone toxicity.

Other Fluoroquinolone Toxicity Effects

In addition to the above-mentioned commonly affected body systems, fluoroquinolone toxicity can cause other serious adverse events in other organ systems. However, systematic review and meta-analysis of studies show mixed results or conflicting evidence for these effects. 

There may be an increased risk of the following with oral fluoroquinolones:

• Aortic aneurysm and dissection.

• Retinal detachment.

• QTc prolongation and cardiac arrhythmia.

• Hepatotoxicity (liver damage).

• Nephrotoxicity (kidney damage).

• Cardiac toxicity (damage to the heart).

• Hypoglycemia and hyperglycemia (changes in blood sugar levels).

• Hemolytic anemia (destruction of red blood cells).

• Coagulopathy (blood clotting problems).

Long-Term Implications of Fluoroquinolone Use

Permanent Disability

Some of the serious adverse reactions linked to fluoroquinolone toxicity can lead to potential permanent disability. These disabling and potentially long-lasting adverse effects include:

• Tendinopathy (tendon disorders), such as tendonitis (inflammation) or tendon rupture.

• Muscle pain and muscle weakness.

• Joint pain and swelling.

• Peripheral neuropathy (abnormal sensations).

• Changes in vision, hearing, taste, or smell.

• Chronic fatigue.

• Sleep problems.

• Central nervous system (CNS) toxicity causing problems with memory.

• Psychiatric effects (depression and anxiety).

Mitochondrial Function and Nervous System 

Fluoroquinolones’ toxicity refers to the risk of serious and potentially irreversible adverse reactions caused by fluoroquinolone treatment. Research suggests that fluoroquinolone toxicity leads to the formation of compounds like aldehyde and peroxynitrite in the body, which cause mitochondrial damage, oxidative stress, and cell death. Fluoroquinolones have been found to be potentially toxic to every organ system in the body, including the musculoskeletal system, nervous system, heart, brain, kidneys, and lungs. 

Effects on the Gastrointestinal Tract

Up to 20% of people treated with fluoroquinolones develop gastrointestinal side effects such as nausea, vomiting, diarrhea, and altered taste. 

Like all antibiotics, fluoroquinolones also carry a risk of Clostridium difficile-associated diarrhea, a type of severe watery or bloody diarrhea that can occur up to 2 months after finishing fluoroquinolone treatment.

Read more: How To Rebuild Your Microbiome After Antibiotics

Case Study

A 28-year-old woman in otherwise good health received levofloxacin 750 mg daily for 7 days to treat a sinus infection. She took the antibiotic without problems. This was followed several weeks later by levofloxacin 750 mg per day for 10 days as prophylaxis (precaution) after she underwent sinus surgery. 

The second course of fluoroquinolone therapy caused a severe drug reaction with symptoms including:

• Severe body-wide tendon, muscle, and joint pain

• Weakness 

• Peripheral neuropathy (abnormal sensations)

• Sensory disturbances

• Cold extremities

• Gastrointestinal side effects

• CNS toxicity, including cognitive effects, sleep problems, mood changes, and confusion

Her primary care doctor advised her to stop the fluoroquinolone antibiotic immediately and to inform all her healthcare providers that she should never receive fluoroquinolones in the future. 

Her symptoms persisted and continued to get worse after stopping treatment. New symptoms emerged, including fatigue, muscle wasting, muscle spasms, shortness of breath, and blood glucose dysregulation. 

The patient remained confined to her bed for a year following treatment with levofloxacin. She was unable to sit up or bear weight on her legs without help. She also required assistance with daily activities such as bathing, using the toilet, and feeding. Her healthcare team was also unsuccessful in managing her pain during the first year. 

For the treatment of fluoroquinolone toxicity, the patient saw a range of specialists, including an internist, neurologist, rheumatologist, endocrinologist, orthopedic surgeon, physical medicine and rehabilitation physician, podiatrist, and physical therapist. 

Clinical Guidelines and Precautions

FDA Warnings and Safety Labeling Updates

If the medication works well, then what’s the problem? Like every drug on the market in the U.S., the FDA takes adverse reports and studies seriously. In 2016 the FDA issued a Safety Announcement stating:

“The U.S. Food and Drug Administration (FDA) approved changes to the labels of fluoroquinolone antibacterial drugs for systemic use (i.e., taken by mouth or by injection). These medicines are associated with disabling and potentially permanent side effects of the tendons, muscles, joints, connective tissue, nerves, and central nervous system that can occur together in the same patient. As a result, we revised the Boxed Warning, FDA’s strongest warning, to address these serious safety issues. We also added a new warning and updated other parts of the drug label, including the patient Medication Guide.”

What Is The New Warning on Fluoroquinolones?

The new warning on fluoroquinolones is a U.S. Food and Drug Administration (FDA) Boxed Warning about serious adverse reactions involving multiple systems in the body, including potentially disabling, long-lasting, and irreversible side effects. The FDA has also advised healthcare providers to limit the use of fluoroquinolone antibiotics for serious infections only and to avoid fluoroquinolones prescribed for mild to moderate infections, using other antibiotics instead.

Alternative Treatments and Safe Use Practices

Previously, fluoroquinolones were widely used to treat urinary tract infections, skin infections, sinus infections, intra-abdominal infections, acute exacerbations of chronic bronchitis, joint infections, and more. Now, they're only recommended by the FDA for certain conditions. 

The FDA warns physicians that fluoroquinolones should not be prescribed when other treatments are possible, because the risks outweigh the benefits. Specifically, other safer antibiotics are recommended for common infections such as sinusitis, bronchitis, and UTIs. If you have any of these infections and your physician recommends taking an antibiotic, be sure to ask what kind of antibiotic they’re prescribing and whether it’s the best option.

Common Questions About Fluoroquinolones

How Toxic Are Fluoroquinolone Antibiotics?

Most people will tolerate a fluoroquinolone antibiotic okay, but these drugs can cause severe adverse reactions in some people. Because of the risk of fluoroquinolone toxicity, these antibiotics are only used to treat serious bacterial infections that cannot be treated with other safer antibiotics.

What Are The Risk Factors for Fluoroquinolone Toxicity?

Anyone can develop fluoroquinolone toxicity; however, some people are at a higher risk. People at an increased risk of serious adverse effects on quinolone antibiotics include:

• Older patients.

• Patients with renal impairment (kidney disease).

• People who have undergone solid organ transplants.

• Concurrent treatment with corticosteroids.

Do Fluoroquinolones Cause Nephrotoxicity?

Yes, fluoroquinolones can cause nephrotoxicity (damage to the kidneys). There are case reports of patients who developed various types of kidney injury after taking fluoroquinolones, including acute drug-induced kidney failure. However, the data regarding fluoroquinolone toxicity on the kidneys is sparse, and the kidney damage may have occurred due to multiple factors in addition to fluoroquinolone antibiotic use. 

Because of the risk of nephrotoxicity and other serious fluoroquinolones side effects like tendonitis and tendon rupture, these drugs should be used with caution in patients with pre-existing kidney disease (renal impairment or reduced kidney function). 

Does Fluoroquinolone Cause Hepatotoxicity?

Yes, a fluoroquinolone may cause hepatotoxicity (liver damage) in a small number of patients. Fluoroquinolone-induced hepatotoxicity may manifest as hepatitis (liver inflammation), pancreatitis (pancreas inflammation), jaundice (yellowing of the skin or whites of the eyes), and hepatic failure (liver failure). Laboratory findings in patients with fluoroquinolone toxicity affecting the liver typically include elevated liver enzymes and bilirubin and prolonged prothrombin time.

Do Fluoroquinolones Cause Tendon Problems?

Yes, fluoroquinolones have been linked to adverse effects involving tendons, including tendonitis (inflammation) and tendon rupture (torn tendon), for example, an Achilles tendon rupture (the large tendon that can be felt like a cord at the back of the ankle). Laboratory experiments have found that fluoroquinolones cause dose-dependent changes in the extracellular matrix, metalloproteinases, signalling proteins, and caspase-3 in human tendon cells.

Which Drug Is A Fluoroquinolone?

Fluoroquinolone antibiotics currently available in the United States include:

• Ciprofloxacin (Cipro)

• Gemifloxacin (Factive)

• Levofloxacin (Levaquin)

• Moxifloxacin (Avelox)

• Norfloxacin (Noroxin)

• Ofloxacin (Floxin)

Note: Enrofloxacin (brand name: Baytril) is a fluoroquinolone antibiotic that is used to treat certain bacterial infections in dogs and cats.

Note: Nalidixic acid was the first quinolone antibiotic discovered in the 1960s and used mainly to treat UTIs. However, the use of nalidixic acid declined because of the development of bacterial resistance and the availability of broader spectrum fluoroquinolones like ciprofloxacin.

Why Were Fluoroquinolones Taken Off The Market?

Many drugs in this class have been withdrawn from the US market because of reports of serious fluoroquinolones toxicity on multiple organ classes, for example:

• Trovafloxacin due to a risk of severe hepatic toxicity.

• Gatifloxacin due to a risk of hypoglycemia and hyperglycemia (changes in blood sugar levels).

• Grepafloxacin because of a risk of cardiac toxicity.

• Temafloxacin because of a risk of nephrotoxicity (acute renal failure), hepatotoxicity (liver damage), hemolytic anemia, coagulopathy (blood clotting problems), and hypoglycemia (low blood sugar).

• Lomefloxacin.

• Sparfloxacin.

• Enoxacin.

What Infections Are Fluoroquinolones Used To Treat?

Fluoroquinolone treatment is reserved for serious infections such as:

• Urinary tract infections caused by Escherichia coli that is resistant to other antibiotics like sulfamethoxazole/trimethoprim

• Bacterial prostatitis

• Salmonella bacteremia

• Typhoid fever

• Infectious diarrhea caused by Campylobacter, Shigella, Salmonella, Vibrios, Yersinia

• Chlamydia trachomatis

• Legionella pneumonia

• Hospital-acquired pneumonia

• Community-acquired pneumonia

• Osteomyelitis

• Meningococcal prophylaxis

• Anthrax prophylaxis 

Related Information and Resources

Further Reading

• Fluoroquinolone antibiotics disabling and potentially long-term adverse effects

• European Medicines Agency (EMA) review

• FDA announcement on fluoroquinolone safety

Recommendations for Patients: Take Warnings and Labels Seriously

The FDA, drug manufacturers, pharmacies, and doctors do their job to keep you safe and healthy up until the medication makes it to your hands. Then the job is yours. 

• Read all information given with your medication by your doctor and pharmacist, as well as the information provided by the manufacturer. 

• Be aware of adverse reactions, so you know to seek medical help before serious damage occurs. 

• It's especially important that you stay vigilant and look for symptoms of tendon rupture and tendonitis.

• Also, watch out for extreme side effects such as depression.

Do not get caught up in trendy or viral opinions that may affect your health and medical treatment. It's always best to consult a licensed physician or pharmacist and do your own research where your health is concerned.