Fluorchinolone

Fluoroquinolones are a class of broad-spectrum antibacterial drugs that inhibit bacterial DNA synthesis by blocking DNA gyrase and topoisomerase IV. They are typically orally bioavailable, distribute well into tissues and fluids, and exhibit bactericidal, concentration-dependent activity. Common agents include ciprofloxacin, levofloxacin, and moxifloxacin.

Pharmacology and spectrum: activity spans many Gram-negative bacteria (including Enterobacterales and, for some agents, Pseudomonas) and certain Gram-positive cocci, with variable activity against anaerobes. Ciprofloxacin tends to be stronger against Gram-negatives; levofloxacin broadens Gram-positive coverage; moxifloxacin has notable anaerobic activity. Individual agents differ in spectrum and adverse effect profiles.

Clinical uses include urinary tract infections and pyelonephritis; complicated intra-abdominal and skin and soft tissue infections; community- and hospital-acquired pneumonia; gonorrhea; prostatitis; and some ocular infections. They may be chosen when first-line agents are unsuitable or when oral therapy with broad coverage is desired, though safety concerns have reduced their use for mild infections.

Adverse effects of fluoroquinolones include tendinopathy and tendon rupture, especially in older patients or those on corticosteroids; central nervous system effects such as confusion or seizures; prolongation of the QT interval and potential cardiac arrhythmias; hypoglycemia or hyperglycemia; and photosensitivity. Absorption can be reduced by divalent or trivalent cations and by sucralfate; avoid use in pregnancy and in children unless specific indications exist.

Resistance develops through mutations in gyrA and parC, plasmid-mediated resistance genes, and efflux pumps. Given safety concerns and rising resistance, fluoroquinolones are recommended to be used judiciously and typically reserved for infections where alternatives are less suitable or where demonstrated benefit outweighs risk.