In a single-dose tolerance and pharmacokinetics study, enoxacin doses ranging from 200 to 1600 mg were administered orally to 12 healthy normal volunteers. Plasma assays demonstrated rapid absorption of enoxacin with first-order elimination and a half-life averaging 3.4-6.4 h. Renal clearance accounted for approximately 40% of total body clearance of drug. In a second placebo-controlled study, 18 normal volunteers received enoxacin in doses of 400, 600 or 800 mg twice daily for 14 days. Plasma concentrations and pharmacokinetic parameters obtained after the first dose were not significantly different from those observed in the single-dose study. With repeated administration, steady-state plasma concentrations were achieved in three days or less. Steady-state pharmacokinetics were characterized by prompt absorption, first-order elimination, and high urinary concentrations of enoxacin. The most frequently-reported adverse experiences involved the gastro-intestinal tract, the central nervous system, and the skin.