Fluoroquinolones

Fluoroquinolones block DNA gyrase and topoisomerase IV, two bacterial type II topoisomerases (gyrase is topoisomerase II). The bacterium needs both to copy, transcribe and repair its DNA, so blocking them halts DNA replication and kills the cell: the drugs are bactericidal. Bacteria resist them mainly through gyrase mutations, a less permeable outer membrane or efflux pumps.

• CiprofloxacinNot a first choice for pneumococcal pneumonia. Levofloxacin and moxifloxacin are licensed for it, including multidrug-resistant pneumococci.
• LevofloxacinWith moxifloxacin, it is one of the two fluoroquinolones WHO recommends in regimens for drug-resistant tuberculosis.
• MoxifloxacinUnlike ciprofloxacin, it covers anaerobes and treats complicated abdominal infections without metronidazole. CDC lists it in regimens for both drug-sensitive and drug-resistant tuberculosis.

• Urinary tract and kidney infections
• Pneumonia
• Complicated abdominal infections
• Skin and soft tissue infections
• Drug-resistant tuberculosis

• Tendinitis and tendon ruptureKnown forSerious
• Long QT interval and torsades de pointesKnown forSerious
• Peripheral neuropathy: tingling, numbness, painSerious
• Confusion, anxiety, depression or psychosisSerious
• Worse muscle weakness in myasthenia gravisSerious
• Aortic aneurysm or dissectionSerious
• Low blood sugar (hypoglycemia)Serious
• High blood sugar (hyperglycemia)
• C. difficile diarrheaSerious
• Sunburn-like reactions in sunlight

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Reserved for sinusitis, bronchitis flares and simple cystitis when no other antibiotic is suitable, because of their serious side effects.
• Antacids, iron, zinc, calcium and dairy foods bind these drugs in the gut and cut absorption, so doses are spaced apart.
• Avoid in myasthenia gravis and in aortic aneurysm; tendon risk rises over 60, with corticosteroids and after organ transplant.
• Children: given only for a few infections, such as anthrax or plague exposure, as they damage growing joints in young animals.

Written for biofideX in plain words, after checking these references:

• Fluoroquinolone Antibiotic (NCI Thesaurus)
• Ciprofloxacin tablets: label (DailyMed)
• Levofloxacin tablets: label (DailyMed)
• WHO consolidated guidelines on tuberculosis: module 4: treatment and care, 2nd edition (WHO)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.