While they were once most well-known for the risk of tendon damage, quinolones are strong antibiotics often used for particularly dangerous diseases. However, as with other types of antibiotics the drug is metabolized through the liver, and one recent study from Canada found that there can be serious risks for acute liver failure and even death for drugs that carry Levaquin side effects and others in the family.

Doctors from the Canadian Drug Safety and Effectiveness Research Network followed more than 100 patients who were admitted to the hospital following reports of acute liver injury. Those who took Levaquin or Avelox have a statistically significant increase in the likelihood of suffering liver failure as a result of taking these antibiotics. Perhaps more distressingly, more than three out of every five patients died as result of the Levaquin side effects and from Avelox.

These drugs have been the subject of litigation regarding the potential for tendon damage noted above. However, they are still used as first-line treatments for some bacterial conditions. This means that while the rates may seem low, with reports of one report of serious side effects per million for Levaqin and six per million for Avelox side effects, the sheer number of patients means that this could affect a large number of people.

Further research into the effects of fluroquinolones will likely be necessary. As the study authors note, “Despite the widespread use of fluoroquinolones, there are few published epidemiologic studies of their safety.” Even their own research was based on a relatively small sample size, so while the statistical significance regarding liver failure is still relevant, having a larger clinical trial would help buttress their conclusions.

It’s also important to note that while the European Medicines Agency has warned that Avelox should only be used when infections are resistant to treatment because of the potential for acute liver failure and related damage, there is no warning to that end in the United States. Drug maker Bayer did work with the U.S. Food and Drug Administration (FDA) to warn of the risks of the potentially deadly skin disorders Stevens-Johnson Syndrome and toxic epidermal necrolysis.

As with liver failure side effects from Zithromax and other antibiotics, it may take weeks or even months to detect the signs of damage. Patients should discuss the risks of these conditions and adverse events with their doctors before beginning treatment, especially if there are alternatives available that don’t carry Avelox side effects. There is little that can be done for people who suffer liver failure except, in some cases, palliative care to limit the pain suffered by a patient.