Fluoroquinolones, a class of synthetic antibacterial drugs, are the only type of drug that directly inhibit bacterial DNA synthesis. Including Cipro, Levaquin and Avelox, they are often prescribed for mild conditions like sinus, urinary tract and ear infections.

Fluoroquinolones, in fact, are some of the most commonly prescribed antibiotics in the United States. However, they carry serious quinolone side effect risks.

According to a study by Dr. Jay Cohen in 2001, fluoroquinolone side effects can touch the nervous system, have musculoskeletal impact, affect the cardiovascular and GI systems and impact the skin. Symptoms can include “memory loss, psychosis, headaches, depression, anxiety, kidney failure, cardiovascular symptoms, nausea and vomiting, blindness and other health problems.”

These are in addition to the tendon damage and peripheral neuropathy fluoroquinolones can cause. Issues were severe enough that Dr. Cohen wrote to his congressman, stating “Most reactions occur very quickly, sometimes with just a few doses of the fluoroquinolone antibiotic. Reactions are acute, severe, frightening, and often disabling. Since the publication of my article with its 45 cases two and a half years ago, I have received e-mails from more than 100 people seeking help for their reactions. In most cases, their doctors have dismissed their complaints or outright denied that the reactions could occur with fluoroquinolones. Yet extensive medical workups do not find any other cause. Worse, there are no known effective treatments. Thus, these people suffer pain and disability for weeks, months, and years.”

In 2013, the U.S. Food and Drug Administration (FDA) released a warning for oral or injectable fluoroquinolone antibiotics, stating they carry a risk for permanent peripheral neuropathy. Peripheral neuropathy is damage to the peripheral nervous system (brain and spinal cord message system). Symptoms vary depending on whether motor, sensory, or autonomic nerves are damaged, but are most frequently felt in the arms and/or legs, categorized by “pain, burning, tingling, numbness, weakness, or a change in sensation to light touch, pain or temperature, or sense of body position.”

The August 2013 warning is not the first FDA warning issued for fluoroquinolones. In 2008, a black box warning was released detailing severe tendinitis and actual tendon ruptures this antibiotic class can cause. (Risks from quinolones have been on their label since 2004, but the severity of reactions forced the label updates.) Other studies showed evidence that fluoroquinolones may increase the risk for acute liver toxicity in individuals over 65, and destabilize blood sugar in diabetics.

Due to these adverse effects, many drugs in the fluoroquinolone family have been removed from the market. Only six remain approved for use, including Ciprofloxacin (Cipro), Levofloxacin (Levaquin), Gemifloxcin (Factive), Moxifloxicin (Avelox), Norfloxicin (Noroxin) and Ofloxicin (Floxin).

Because of the extreme health risks connected to fluoroquinolones, it has been recommended that they should only be used to treat serious bacterial infections that won’t respond to any other treatment.

Fluoroquinolones and Peripheral Neuropathy

Fluoroquinolones are antibiotics with an attached fluorine molecule. This molecule enables the medication “to penetrate into sensitive tissues like [the] brain and central nervous system, where they can exert neurotoxic effects.”

The National Institute of Neurological Disorders and Stroke estimate that close to 20 million people in the U.S. suffer some form of peripheral neuropathy. Causes of peripheral neuropathy can include alcoholism, autoimmune diseases, diabetes, and a host of other factors. Fluoroquinolones fall into this list as medication toxicity is listed as a possible cause.

Diagnosis requires a “thorough neurological examination … to sort out the cause of the symptoms and involves taking an extensive medical history (covering symptoms, work environment, social habits, exposure to toxins, alcohol use, risk of HIV or other infectious diseases, and family history of neurological diseases). In addition, tests are usually performed to identify the cause of the neuropathy as well as the extent and type of nerve damage.” In the case of drug-induced peripheral neuropathy, the National Institute of Neurological Disorders and Stroke suggests that it may be resolved “when these medications are discontinued or dosages are adjusted,” but this is only if caught in time.

Of the quinolones, Levaquin was the best selling in 2010. However, it was named in more than 2,000 lawsuits by 2011 over severe reactions.