Pharmacology
Summary
Fluoroquinolones are a very important class of antibiotics, and include levofloxacin and ciprofloxacin. They are used to treat various Gram-negative and Gram-positive bacterial infections, most notably in the urinary tract and gastrointestinal pathways, including complicated UTIs and pyelonephritis. They function by inhibiting bacterial topoisomerases, such as DNA gyrase, preventing normal transcription and replication, thereby killing the bacterium (fluoroquinolones are bactericidal).
Fluoroquinolones may be used for Pseudomonas coverage in high-risk patients in hospital settings—those who are immunocompromised or have received urinary tract instrumentation and are at risk for UTIs caused by pseudomonas. Fluoroquinolones also penetrate well into bone, even with oral administration, and are therefore used to treat Gram-negative osteomyelitis. They are effective in treating bacterial diarrhea caused by numerous Gram-negative GI pathogens, such as Shigella, Salmonella, E. coli, and Campylobacter, and the Gram-positive pathogen Bacillus anthracis. Fluoroquinolones, when taken orally, can have their absorption impaired by divalent and trivalent cations, such as calcium, magnesium, and iron. Adverse effects of fluoroquinolones include nausea, vomiting, diarrhea, tendon rupture, cartilage damage, and damage to growing cartilage leading to arthropathy in children less than 10 years of age. Avoid use of quinolones during pregnancy and in elderly patients, especially those on steroids.
Lesson Outline
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FAQs
Fluoroquinolones are primarily used to treat gram negative bacterial infections. They are especially effective for urinary tract infections caused by bacteria such as E. coli and Proteus. Levofloxacin and ciprofloxacin are often used to treat UTIs caused by Pseudomonas (when susceptible). They are also used as an empiric treatment for pyelonephritis and acute prostatitis, and for treating Salmonella gastroenteritis and gram negative bacterial causes of gastroenteritis (e.g. Shigella, Salmonella, E. coli, Campylobacter).
Fluoroquinolones work by inhibiting bacterial topoisomerases, such as DNA gyrase. This inhibition disrupts the bacteria's ability to replicate and repair DNA, thus leading to the death of the bacterial cells.
Yes, fluoroquinolones have been associated with certain risks. There is a risk of prolonged QT interval. They can also cause gastrointestinal side effects such as nausea, vomiting, and diarrhea. In some cases, fluoroquinolones have been associated with tendon and cartilage damage, particularly in the elderly and with chronic steroid use. Babies and children under 10 years old are at increased risk of damage to growing cartilage, so fluoroquinolones are not generally recommended for these age groups.
Divalent and trivalent cations, such as calcium, iron, and magnesium, can decrease the absorption of fluoroquinolones. These elements can bind to the fluoroquinolones, forming complex ions that are poorly absorbed in the intestines. It's typically recommended that patients take fluoroquinolones either 2 hours before or 4 to 6 hours after consuming these minerals.
Respiratory quinolones like levofloxacin and moxifloxacin are specifically used to treat respiratory tract infections. They are effective in treating community-acquired and atypical pneumonia, often termed "walking" pneumonia, caused by bacteria such as Mycoplasma pneumoniae and Legionella pneumophila.
