Fluoroquinolones and the risk for tendon injury

Fluoroquinolones are a commonly used antibiotic that is widely used to treat a variety of illnesses caused by infections such as respiratory and urinary tract infections. In the USA it has been estimated that fluoroquinolones are the third most commonly prescribed drug in the antibiotic class. The precursor of this drug category, nalidixic acid is considered the first quinolone drug even though it is not strictly a fluoroquinolone. It was first introduced in 1962 for the treatment of urinary tract infections. Now the Federal Drug Administration in the USA has approved many fluoroquinolones including levofloxacin (Levaquin), ciprofloxacin (Cipro), moxifloxacin (Avelox), ofloxacin, gemifloxacin (Factive) and delafloxacin (Baxdela).

The fluoroquinolone antibiotics work against infections caused by bacteria by interfering with the bacteria’s DNA replication. Early generation fluoroquinolones hamper bacterial DNA synthesis during replication primarily by inhibiting DNA gyrase, one enzyme that is required for bacterial DNA replication, but does not affect human cells. There are several generations of the fluoroquinolones that are available, with each subsequent generation being a refinement of the generation before. The earlier generation fluoroquinolones were, in general, more narrower spectrum than the subsequent ones, which means the more recent ones are more effective against a wider range of types of bacteria.

Fluoroquinolones are generally considered to be very safe antibiotics which do not cause many serious or life-threatening adverse reactions. Like all drugs they do have side effects that are not common and are usually easily managed. The most frequent side-effects are gastrointestinal reactions (such as nausea, dyspepsia and vomiting) and central nervous system reactions such as dizziness, insomnia and headache. Anyone starting on these drugs should be monitoring for these potential side affects.

One unique side affect of the Fluoroquinolones is a higher risk of tendonitis and tendon ruptures, especially of the Achilles tendon. This has been most commonly documented with the use of ciprofloxacin and levofloxacin. The tendonitis typically appears within a month or so of starting to take the drug. However, the tendon ruptures can occur suddenly and often do not have any noticeable symptoms before they happen.

A recent study from from Jichi Medical University in Tochigi, Japan, suggests that the newer third-generation fluoroquinolones may have a lower risk of Achilles tendon rupture. These researchers used a health care administrative database to identify 504 patient cases of Achilles tendon ruptures that were also taking an antibiotic. They were able to find that these third-generation fluoroquinolones were not associated with an increase in Achilles tendon rupture. The database revealed that the commonly used first- and second-generation fluoroquinolones, such as ciprofloxacin were at elevated risk of an Achilles tendon rupture, which previous research has shown. The newer third-generation fluoroquinolones such as moxifloxacin, garenoxacin, sitafloxacin, prulifloxacin and pazufloxacin were associated with a lower risk of developing a tendon rupture. They did note that they did not investigate the other side affects of this drug and further research is needed to properly evaluate that risk.

The fluoroquinolones remain an important antibiotic for use against susceptible infections in those with respiratory and urinary tract infections with limited side affects.

Craig Payne is a University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger and a dad.