Fluoroquinolones, also called Quinolones, are a group of antibiotics helpful for treating gram-negative and gram-positive bacterial infections.
The gram-negative infections this group treats include Haemophilus influenzae, Neisseria gonorrhoeae, Chlamydia, Escherichia coli, Klebsiella pneumoniae, Salmonella, Pseudomonas aeruginosa etc.
And the gram-positive infections include Streptococcus pneumoniae, Enterococcus, Staphylococcus aureus etc.
Because this antibiotic group can target the bacteria above, they are used to treat infections that affect the urinary tract, respiratory system, skin, pelvic, abdominal, joint, and bone areas.
What medications are considered Fluoroquinolones?
Ofloxacin
Norfloxacin
Ciprofloxacin
Gemifloxacin*
Levofloxacin*
Moxifloxacin*
Delafloxacin*
Remember that the generic name of a Quinolone ends with floxacin.
*newer Quinolones of the group that have a wider antimicrobial reach
How are Quinolones Administered?
Orally (absorbed very well in the gut) or parenterally
Fluoroquinolones Mechanism of Action?
Fluoroquinolones have the ability to kill bacteria. Therefore, they are known as being bactericidal.
They do this by inhibiting the bacteria’s DNA replication process (hence inhibit bacterial DNA synthesis). To do this, they target two main enzymes that play a role in this DNA replication process called DNA gyrase and Topoisomerase IV.
First, let’s simplify the DNA replication process that bacteria undergo. The bacterium has circular double-stranded DNA inside itself that it wants to make copies of so it can make more bacteria.
To make these copies, the double-stranded DNA must loosen itself and create easy access to the individual strands so copies can be made of each strand (remember double-stranded DNA is normally wrapped around it itself).
Therefore, to loosen the strands the enzymes known as helicase loosen the connection. Once loosen, another enzyme called DNA polymerase comes along and makes copies of each of those strands. Now, there are two copies made.
However, the part of the DNA strand that wasn’t separated by the helicases have become supercoiled (think of it as these two strands being very tightly wrapped around each other). To decrease this supercoiling, the enzyme DNA gyrase comes in and loosens the strands by slicing and reconnecting parts of it.
Once negative supercoiling has occurred, by the help of DNA gyrase, the two new copies fold over into a circular pattern in preparation for separation. In order to separate and become individual chromosomes, the copies must be separated by the enzyme Topoisomerase IV.
So, now that we’ve simplified the bacterial DNA replication process, let’s talk about how Quinolones disrupt this process.
Now depending on what type of bacteria we’re dealing with, like gram-positive or negative, the Fluoroquinolone will mainly target a certain enzyme like either DNA gyrase or Topoisomerase IV.
For example, with many gram-negative bacteria the Fluoroquinolone will target DNA gyrase, which affects the negative supercoiling process. If the double-DNA stranded can’t “unsupercoil”, it can’t continue with the DNA replication process, hence dies.
For gram-positive bacteria, the Fluoroquinolone will target the enzyme Topoisomerase IV, which will prevent the separation of the new daughter DNA strands, hence preventing replication and causing the death of the bacteria.
Nursing Considerations for Fluoroquinolones?
Before administering these antibiotics always check the patient’s allergies and obtain cultures, if needed before administration.
During administration monitor the effectiveness of the antibiotic….is the antibiotic working? Is the patient getting better? Is the patient afebrile, has a normalizing white blood cell count, vital signs within normal limits (no hypotension, tachycardia), no mental status changes or respiratory distress?
In addition, the nurse wants to monitor for potential adverse effects. To help us remember the main concepts, let’s remember the mnemonic:
FLOXACINS
Fluid intake important, especially with Cipro!
- Instruct the patient to take the medication with at least 8 oz. of water and to drink fluids (around 2 Liters per day if not contraindicated) throughout the day to prevent crystalluria. Crystalluria is the formation of crystals in the urine, which happens because the medication causes the urine to become alkaline. As a side note: Sulfonamides (another group of antibiotics) can lead to this too.
- Crystalluria can lead to a blockage in the kidney which will result in kidney injury and renal failure
- Nursing interventions: monitor urinary output (30 mL/hr in adults), keep track of patient’s intake and output, monitor renal function (BUN and creatinine)
Long QT Interval
- Quinolones can prolong the QT interval, and this increases the risk of a lethal rhythm called Torsades de pointe. The risk is increased if the patient is taking a Quinolone along with another medication that can prolong QT interval (ex: Amiodarone).
Older adults ( >60 or older) are at risk for tendon inflammation and rupture, especially with the Achilles tendon usually being involved.
- The risk is increased with advanced age, if the patient is taking corticosteroids and has a history of diabetes/renal issues.
- Educate patient to immediately report pain, swelling, snap feeling or immobility of a tendon.
X (don’t) administer with (or at the same time) medications that contain cations like (calcium, zinc, iron, magnesium, aluminum…these are ingredients in antacids/vitamins) or with dairy products (ex: milk, cheese, yogurt) because they decrease the absorption of oral quinolones.
- Administer oral quinolones 2 hours before or after meals
- Administer oral quinolones 6 hours after administering an antacid or 2 hours before an antacid
Avoid in children and pregnancy (in children it can cause bone and cartilage problems)
C. diff (a superinfection in the gut): it occurs from taking certain groups of antibiotics like Quinolones and it can develop while the patient is taking the medication or after. Signs and symptoms include a fever, watery diarrhea, and abdominal pain. Notify the physician who will order a stool culture that will test the stool for this infection.
Interactions with Quniolones
- Big ones include: Caffeine, Phenytoin, Warfarin, Theophylline, antiarrhythmics (Amiodarone) and the interaction causes increased side effects of these medications.
Neuromuscular exacerbation: can make neuromuscular disorders worst like myasthenia gravis. The nurse should monitor for muscle weakness.
Sun sensitivity
- These medications can increase the skin’s sensitivity to burns and blistering from the sun’s rays. Educate the patient to take precautions when going outdoors. This can happen while taking the medication and several days afterwards.
Now test your knowledge with this Fluoroquinolones Quiz.
References
Center for Drug Evaluation and Research. (2022, January 22). FDA updates warnings for oral and injectable fluoroquinolone antibiotics due to disabling side effects. U.S. Food and Drug Administration. Retrieved November 3, 2022, from https://www.fda.gov/drugs/fda-drug-safety-podcasts/fda-drug-safety-podcast-fda-updates-warnings-oral-and-injectable-fluoroquinolone-antibiotics due#:~:text=Fluoroquinolone%20labels%20already%20have%20a,peripheral%20neuropathy%20and%20CNS%20effects.
Paton JH, Reeves DS. Fluoroquinolone antibiotics. Microbiology, pharmacokinetics and clinical use. Drugs. 1988 Aug;36(2):193-228. doi: 10.2165/00003495-198836020-00004. PMID: 3053126.
Van der Linden PD, Sturkenboom MCJM, Herings RMC, Leufkens HMG, Rowlands S, Stricker BHC. Increased Risk of Achilles Tendon Rupture With Quinolone Antibacterial Use, Especially in Elderly Patients Taking Oral Corticosteroids. Arch Intern Med. 2003;163(15):1801–1807. doi:10.1001/archinte.163.15.1801