What Is Fluoroquinolone Toxicity, and What Causes It?
Key takeaways:
Fluoroquinolones are a type of antibiotic used to treat many bacterial infections.
Their potential side effects are minor in most people. But, in some cases, fluoroquinolones can cause disabling and sometimes irreversible toxicity.
Fluoroquinolone-associated disability (FQAD) is when these toxicities are severe and affect several different parts of your body.
You may have heard of fluoroquinolones (sometimes also called quinolones). They’re a group of antibiotics that can treat common bacterial infections. Like most medications, fluoroquinolones can cause minor side effects. But, for some, these side effects are severe.
From 1997 to 2015, 178 healthy people reported to the FDA that they took an oral fluoroquinolone and developed severe side effects. These side effects were present in many parts of the body. This phenomenon is now known as fluoroquinolone-associated disability (FQAD).
Since then, the FDA has issued several warnings about fluoroquinolone toxicity. Below, we’ll discuss side effects that can occur from taking fluoroquinolones. We'll also cover how to avoid fluoroquinolone toxicity and how to tell if you might have it.
What are fluoroquinolones?
Fluoroquinolones are a group of antibiotic medications. They kill bacteria by stopping them from copying themselves.
Examples of fluoroquinolone antibiotics include:
Ciprofloxacin (Cipro)
Levofloxacin (Levaquin)
Moxifloxacin (Avelox)
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They’re effective at treating many bacterial infections, including:
Bone and joint infections
Certain sexually transmitted infections (STIs)
Gastrointestinal (GI) tract and stomach infections
Pneumonia
Skin infections
Urinary tract infections (UTIs)
What is fluoroquinolone toxicity, and what kind of damage can it cause?
Fluoroquinolones can cause mild side effects including nausea, diarrhea, and vomiting. In rare cases, these medications can cause more serious side effects. This can involve the tendons, muscles, heart, and nerves. These are signs of fluoroquinolone toxicity.
Some of these serious side effects can occur as a result of taking fluoroquinolones. But when multiple parts of your body are affected, it’s referred to as FQAD. More on that next.
Because of these severe side effects, the FDA enhanced warnings about fluoroquinolone toxicity. They recommended not prescribing fluoroquinolones unless there’s no other medication option.
Fluoroquinolone toxicity hasn’t been associated with eye or ear drops. So, we'll focus only on oral and injectable forms.
Fluoroquinolone-associated disability (FQAD)
In 2013, the FDA evaluated reports of healthy people experiencing FQAD. FQAD is sometimes referred to as “being floxed.”
The FDA found that FQAD symptoms can appear within hours to weeks of taking a fluoroquinolone. Side effects lasted 14 months, on average. But, some people reported symptoms lasting 9 years. Several people reported that FQAD symptoms went away after stopping the fluoroquinolone. But others experienced continued side effects even after stopping the medication.
FQAD can affect your tendons, muscles, joints, nerves, and brain. According to the FDA, you may have FQAD if your side effects last at least 30 days after your last dose.
The side effects must be disabling, in at least two areas of the body, including the:
Muscles and tendons: muscle or joint pain and tendonitis/tendon rupture
Spinal cord and nerves: nerve damage and twitching
Brain: anxiety, depression, hallucinations, and memory problems
Senses: eye pain, vision loss, ringing in your ears, hearing loss, and loss of smell
Heart: chest pain or skipping heartbeats, known as palpitations
Your risk for FQAD goes up if you take fluoroquinolones at high doses or for long periods of time. But it’s unknown how long is considered “too long.” Taking a fluoroquinolone many times within a short timeframe also raises your risk.
Tendonitis and tendon rupture
Tendons are flexible tissues that connect your muscles to your bones. For example, the Achilles tendon connects the muscles in your calf to your heel bone. Using a fluoroquinolone can cause tendonitis (tendon inflammation). This can raise the risk of tendon rupture, which is a partial or complete tear of a tendon.
Achilles tendon rupture is the most common tendon rupture associated with fluoroquinolone toxicity. When fluoroquinolones cause tendon rupture, it usually affects both sides of your body.
Tendonitis or tendon rupture can be a symptom of FQAD. It can also be an independent side effect of fluoroquinolones. In 2008, the FDA added a boxed warning about this risk to all fluoroquinolones. A boxed warning is the most serious warning the FDA can give a medication.
Certain factors can raise your risk for tendon rupture if you use a fluoroquinolone. These can include:
Age over 60 years old
Being an athlete
Using a corticosteroid, like prednisone
Having certain medical conditions, including high cholesterol, end-stage kidney disease, and rheumatoid arthritis
Symptoms of tendonitis include inflammation, pain, and swelling in a tendon. Signs of tendon rupture include hearing a “pop” or “snap” sound and feeling pain in the affected area.
Immediately contact your healthcare provider if you notice these symptoms. They will likely tell you to stop taking the fluoroquinolone. You should also rest the affected tendon until your provider can examine you.
Nervous system side effects
Fluoroquinolones can cause side effects involving your nervous system. Like tendonitis and tendon rupture, these effects can be symptoms of FQAD or exist on their own.
Peripheral neuropathy
Fluoroquinolone toxicity can cause irreversible nerve damage. In 2013, the FDA added a boxed warning for nerve damage to all oral or injectable fluoroquinolones.
The most common form of nerve damage caused by fluoroquinolones is peripheral neuropathy. This is nerve damage that affects your arms and legs. It can occur at any time after starting a fluoroquinolone.
Symptoms of peripheral neuropathy include the following feelings in your arms or legs:
Burning
Changes in the way you feel sensations like touch and temperature
Numbness
Pain
Tingling
Weakness
Contact your healthcare provider immediately if you develop any symptoms listed above.
Central nervous system toxicity
Fluoroquinolones can cause central nervous system (CNS) toxicity. Your CNS includes your brain and spinal cord. The CNS sends messages to control mental and physical processes throughout your body.
CNS toxicity can cause:
Anxiety
Confusion
Depression
Hallucinations
Suicidal thoughts
If you develop signs of CNS toxicity, contact your healthcare provider right away. If you or someone you know is having thoughts of suicide, you’re not alone and help is available. Call the National Suicide Prevention Lifeline at 1-800-273-8255, or text HOME to 741-741 to reach the Crisis Text Line.
Heart problems
Fluoroquinolone toxicity can also affect your heart. Though rare, fluoroquinolones can cause long QT syndrome. The QT interval is a period in time after each heartbeat where your heart’s electrical activity resets. In long QT syndrome, the QT interval becomes longer than normal. This can cause abnormal or chaotic heartbeats. Long QT syndrome can cause life-threatening heart arrhythmias.
Symptoms of a long QT interval can include:
Blurry vision
Lightheadedness
Seizures
Fainting, especially when emotionally excited or physically active
Call 911 or seek emergency medical attention if you’re experiencing any of these symptoms.
What should I do if I experience fluoroquinolone toxicity?
Contact your healthcare provider immediately if you experience the side effects we’ve covered. They should have you stop taking the fluoroquinolone immediately. If it’s confirmed that you have fluoroquinolone toxicity, you should avoid using these medications in the future.
Unfortunately, stopping the fluoroquinolone doesn’t guarantee that your symptoms will go away. There’s very little information on treating FQAD and its long-term symptoms. Scientists are still learning about the condition, including why certain people experience it and possible treatments.
How can I avoid fluoroquinolone toxicity?
The best way to prevent fluoroquinolone toxicity is to avoid using them. That is, unless no other antibiotic will work to treat your infection.
Here are some general tips on avoiding fluoroquinolone toxicity:
Talk to your healthcare provider about other treatment options if you’re an athlete or are very physically active. You’re at higher risk for tendon rupture if you use a fluoroquinolone and do strenuous exercise. If you need fluoroquinolones, consider stopping exercise until after you finish taking them.
Tell your healthcare provider or pharmacist about all your medications, including over-the-counter products. They can check for any interactions that could raise your risk for toxicity.
Tell your healthcare provider and pharmacist about any medical conditions you have. Some (such as chronic kidney disease) may raise your risk for fluoroquinolone toxicity.
The bottom line
Many people are able to use fluoroquinolones and experience only mild side effects. But some may experience damaging or permanent side effects. This is called fluoroquinolone toxicity. When they’re severe and several different organ systems are involved, it’s called FQAD.
Treatment and recovery options are not yet well understood. It’s best to avoid fluoroquinolones if another antibiotic can treat your infection.
If you notice serious side effects while taking a fluoroquinolone, contact your provider right away. They can recommend a different antibiotic if fluoroquinolone toxicity is confirmed.
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References
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Food and Drug Administration. (2013). FDA requires label changes to warn of risk for possibly permanent nerve damage from antibacterial fluoroquinolone drugs taken by mouth or by injection.
Food and Drug Administration. (2017). Fluoroquinolone safety label changes (Powerpoint presentation).
Food and Drug Administration. (2018). FDA Drug Safety Communication: FDA updates warnings for oral and injectable fluoroquinolone antibiotics due to disabling side effects.
Food and Drug Administration. (2020). FDA updates warnings for fluoroquinolone antibiotics.
Kohanski, M., et al. (2010). How antibiotics kill bacteria: from targets to networks. Nature Reviews Microbiology.
Ludwig PE., et al. (2021). Neuroanatomy, Central Nervous System (CNS). StatPearls.
Michalak, K., et al. (2017). Treatment of the Fluoroquinolone-Associated Disability: The Pathobiochemical Implications. Oxidative medicine and cellular longevity.
Medline Plus. (2020). Achilles Tendon Rupture.
Morales D., et al. (2019). Association Between Peripheral Neuropathy and Exposure to Oral Fluoroquinolone or Amoxicillin-Clavulanate Therapy. JAMA Neurology.
Yan, A., et al. (2021). Quinolones. StatPearls.
