Hey this is Dr K from imedicalschool here to talk about a class of antibiotics called
fluoroquinolones.
The fluoroquinolones that are commenly used within the outpatient and inpatient setting
include ofloxacin, ciprofloxacin, levofloxacin, moxifloxacin and norfloxacin.
The flurorquinolone groups of antibiotics have an interesting property compared to other
antibiotics as these are the only antibiotics that directly inhibit bacterial DNA synthesis.
How do the fluoruquinolones inhibit bacterial DNA synthesis?
Well these antibiotics work on the enzymes DNA gyrase and topoisomerase four.
These enzymes are involved in the winding and unwinding of DNA.
DNA gyrase and topoisomerase four aid the unwinding of DNA so it can be read and replicated.
With the inhibition of these enzymes, bacteria are unable to replicate and more importantly
are unable to produce proteins that they need for survival.
As a result the fluorquinolone class of antibiotics are bacteriacidal meaning they actually lead
to bacteria cell death.
Now what organisms are targeted by fluoruquinolone antibiotics?
All the fluoruquinolones generally affect aerobic gram negative bacilli and gram negative
cocci.
Examples of gram negative bacilli include enterobacteriaceia and haemophilus.
Examples of gram negative cocci include Neisseria and Moraxella.
In addition fluoruquinolones can also work against pseudomonas and staph aureus.
Now the strength of each of the fluoruquinolones on bacteria vary from each medication.
For example norfloxacin, ciprofloxacin, and ofloxacin have poor activity against streptococci
and many anaerobes.
Moxifloxacin has greater activity against anaerobes.
Both levofloxacin and moxifloxacn have good activity against gram positive cocci.
In terms of treating Pseudomonas, ciprofloxacin tends to have the best activity against pseudomonas
. Moxifloxacin and levofloxacin tend to have less anti-pseudomonal activity.
Now ciprofloxacin is so frequently used that many areas of the country have seen a significant
surge of pseudomonas resistance to ciprofloxacin so it is important to know what are the bacterial
resistances that are present in your community.
In terms fo respiratory infections all the fluoruuquinolones are generally efffecive,
however, both levofloxain and moxifloxacin have better strep pneumoniae coverage than
the other fluoruoquinolones.
Now that we talked about the bacterial coverage of the fluoroquinolones it is important to
talk about how these drugs are absorbed and cleared from the body.
Fluorquinolones are absorbed well in the upper gastrointestinal tract.
One of their advantages is that they have a bioavailability that exceeds 50 percent
and actually reaches 100 percent in some.
Meaning for some fluoroquinolones administering iV provides no greater bioavailability than
administering it orally.
Specifically bioavalabiltiy for ciprofloxain is 70%, > 95 percent for ofloxacin and levofloxacin
with greater than 85 percent bioavailability for moxifloxacin
Though the fluoroquinolones are absorbed through the GI tract they have different routes of
elimination.
Ofloxacin and levofloxacin are renally eliminated.
Moxifloxacin is eliminated predominately by the liver and ciprofloxacin is excreted by
both pathways
It is important when administering any medication that one understands the risks and adverse
effects of the medication.
In pregnant women Fluoroquinolones have not been established as safe and more research
needs to be done.
That being said quinolones should be avoided in children less than 18 ears old because
there have been reports of joint cartilage erosions in animal studies . The concerns
are these antibiotics can lead to detrimental outcomes on a child's growth.
What are the side effects associated with fluoruoquibnolone use?
Fluoruquinolones are associated with an increase risk of developing c. diff colitis as these
antibiotics clear the normal bowel flora.
More recently Fluoroquinolones have been found to cause a peripheral neuropathy.
If this occurs they should be stopped and switched to a different class of antibiotics.
The neuropathy can last for months to years and occasionally can be permanent.
Fluoruquinolones have been associated with tendinopathy and tendon rupture.
Those highest at risk were greater than 60 years old, nonobese, female, and we're using
glucocorticoids
In addition to tendinopathy, Fluoroquinolones cause QT interval prolongation due to inhibition
of potassium channels.
Moxifloxacin and ciprofolaxin were associated with increase rates of cardiac arrythmias
though ciprofloxacn was not associated with an increase in cardiovascular mortality Patients
who are elderly, female or have QT prolongation at baseline are at the greatest risk.
Rarely hepatotoxicity can occur due to fluourquinolones and in some cases even lead to retinal detachment.
Well that was a brief review of the fluoroquinlones, I hope you enjoyed this video and if you did
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This is Dr K and I will see you next time.