54. Antibiotics for UTIs

Antimicrobial selection for urinary tract infections (UTIs) relies heavily on the unique pharmacological property of high urinary drug concentration, which often exceeds plasma levels by orders of magnitude. This concentration effect allows for the effective treatment of pathogens—including *Pseudomonas aeruginosa*—even when standard plasma-based breakpoints suggest resistance. While clinical guidelines provide a necessary foundation for empirical therapy, infection specialists must balance broad-spectrum coverage against the risks of promoting antimicrobial resistance. Evidence supports shorter treatment durations for most UTIs, with five to seven days often proving sufficient for pyelonephritis in the absence of complicating factors like stones or stents. Furthermore, agents such as fosfomycin and doxycycline offer viable, narrow-spectrum alternatives for difficult-to-treat infections, provided clinicians account for the specific pharmacokinetic profiles that enable these drugs to overcome traditional susceptibility thresholds within the urinary tract.