The Findings: Children and adults treated with five classes of oral antibiotics have a significantly higher risk of developing kidney stones. The five classes include oral sulfas, cephalosporins, fluoroquinolones, nitrofurantoin, and broad-spectrum penicillins. Patients who received sulfa drugs were more than twice as likely as those not exposed to antibiotics to have kidney stones. For broad-spectrum penicillins, the increased risk was 27 percent higher. The strongest risks appeared at younger ages and among patients most recently exposed to antibiotics. The risk of kidney stones decreased over time but remained elevated several years after antibiotic use.