Single doses of 250 and 500 mg of BL-S 578 (cefadroxil), a new semisynthetic cephalosporin, were orally administered to 13 normal, healthy volunteers and serum levels determined at timed intervals for 7 h. Peak concentration was obtained at 1½ h after administration of 250 mg (8.981 μg/ml) or 500 mg (17.861 μg/ml). Urinary excretion levels within 24 h after ingestion of single doses of 250 and 500 mg of cefadroxil were 89.92 and 86.34%, respective