Pharmacotherapy Newsletter

Volume 1, Issue 33, 08/31/2009

Question

What is the mechanism by which the fluoroquinolone antibiotics (e.g., ciprofloxacin, gemifloxacin, levofloxacin, moxifloxacin) can increase a patient's risk for developing a seizure or worsen epilepsy?

Answer

The fluoroquinolone antibiotics are commonly used in clinical practice for a number of conditions but most frequently are used to treat upper and lower respiratory tract infections (e.g., bacterial sinusitis, nosocomial and community acquired pneumonia), prostatitis and urinary tract infections (both pyelonephritis and cystitis).(1-5)  Several fluoroquinolone antibiotics have been taken off the market, but those that remain include, ciprofloxacin (Cipro®), gemifloxacin (Factive®), levofloxacin (Levaquin®), moxifloxacin (Avelox®), norfloxacin (Noroxin®), and ofloxacin (Floxin®).(1-5)  Many of the above medical conditions can occur in a wide group of patients including those patients already taking medications that have been associated with causing seizures or in patients who already have an underlying seizure disorder or epilepsy.  While the overall incidence of central nervous system (CNS) side effects is low (1-4%), convulsive seizures have been reported in patients taking fluoroquinolones, especially if they are also taking nonsteroidal antiinflammatory drugs (NSAIDs).(6-8)   As a result, the Food and Drug Administration (FDA) approved product package inserts currently warn healthcare providers about the risk for various CNS side effects (tremors, restlessness, anxiety, confusion, paranoia, insomnia, etc.) as well as an increased risk for seizures.(1-5,8)

What effect do fluoroquinolone antibiotics have on the CNS to cause these side effects?
Considering all of the signs and symptoms mentioned in the manufacturers' warnings, the answer is multifactorial.  One contributing factor is the ability of fluoroquinolones to modulate the activity of the.....

The complete answer for this issue also comes with a figure that shows the proposed mechanism for fluoroquinolone induced seizures. 

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