One of the major advances in modern medicine was the development of antimicrobial chemotherapy. However, many antibacterial agents have unexpected or undesirable nonantimicrobial effects on humans. Microbes and man share many essentials of life, including DNA, adenosine triphosphate, and other biochemical pathways. Hence, some of these nonantimicrobial effects may also turn out to be pharmacologically useful. Oral hypoglycemic agents (i.e., sulfonylureas) and a certain diuretic agent (acetazolamide) are derivatives of sulfonamides. Erythromycin has been used clinically for its stimulatory effect on gastrointestinal motility. Macrolides, lincosamides, and tetracyclines have been known for their immunomodulatory effects. A tetracycline has been used to treat the syndrome of inappropriate antidiuretic hormone. Aminoglycosides may influence mucus production in patients with cystic fibrosis. Other antimicrobials may have side effects that are not therapeutically useful, such as osmotic diuresis with high-dose beta -lactam administration, neuromuscular blockade of aminoglycosides, dysglycemia of fluoroquinolones, and serotonin syndrome with oxazolidinones.