Ciprofloxacin tablets. Photo credit: Wikimedia commons.
Ciprofloxacin tablets. Photo credit: Wikimedia commons.

Fluoroquinolones are the third most commonly prescribed family of antibiotics in the U.S. for adults, and, in my opinion, the second most fun to say (right behind aminoglycosides). Fluoroquinolones include levofloxacin (Levaquin), ciprofloxacin (Cipro), moxifloxacin (Avelox), ofloxacin, and delafloxacin. Their popularity is well earned; they’re very effective at treating certain bacterial infections. But since their discovery in the late 1970s, increasing concern has been raised about their safety.

In 2008, the FDA warned about the risk of tendinitis and tendon rupture in patients taking fluoroquinolones. This happened quite rarely, but frequently enough that reports caught the FDA’s attention. In 2011 it was noted that some patients with myasthenia gravis had worsening of their symptoms on these antibiotics. In 2013 the FDA updated these warnings to add the possibility of irreversible peripheral neuropathy (nerve damage) while taking fluoroquinolones.

All medications have some side effects, and these serious side effects are relatively rare, but their severity and the fact that they persist long after the medication is stopped (and in some cases are permanent) raised concern.

There are some other risks of fluoroquinolones that we’ve known over the years. Like many other families of antibiotics, they can lead to Clostridium difficile colitis, a dangerous intestinal infection about which I’ve written many posts. Fluoroquinolones, like a few other antibiotic families, can predispose to dangerous and even fatal heart rhythm abnormalities.

In July, the FDA issued warnings about two additional adverse effects that have been reported in patients taking fluoroquinolones. The first side effect is psychiatric, causing disturbances in attention, disorientation, agitation, nervousness, memory impairment, and delirium. This has been reported after even just one dose of the medication. The second adverse effect is hypoglycemic coma, coma due to dangerously low blood sugar. This happens more frequently in elderly patients and in patients taking diabetes medications that lower blood sugar.

The FDA recommends that fluoroquinolones be avoided in patients with uncomplicated bladder infections, sinus infections, or emphysema exacerbations, unless no other antibiotic alternatives are available. They also recommend that elderly patients and patients with diabetes who are prescribed fluoroquinolones be warned about the symptoms of low blood sugar and that blood sugar be monitored in these patients. Patients should also we advised about the risk of psychiatric side effects.

Of course, one of the easiest ways to minimize the side effects of antibiotics is to avoid antibiotics altogether when they are not beneficial. Many antibiotic prescriptions are written for colds (a viral illness for which antibiotics don’t help), for acute bronchitis (also almost always caused by viruses), and for sinus infections (for which decongestants and pain relievers usually suffice).

If antibiotics are needed, fluoroquinolones should be reserved for cases in which other alternatives are absent, or for severe infections for which the broad spectrum and effectiveness of fluoroquinolones can be life-saving.

Learn more:
FDA updates warnings for fluoroquinolone antibiotics on risks of mental health and low blood sugar adverse reactions (FDA News Release)
Thinking of a Fluoroquinolone? Think Again (Medscape)
When antibiotics turn toxic (Nature, news feature)
In Brief: More Fluoroquinolone Warnings (The Medical Letter on Drugs and Therapeutics, by subscription only)

My previous posts about Clostridium difficile