Plasma cocaine levels were determined in 7 subjects after intranasal and oral cocaine. Intranasal doses of 0.19, 0.38, 0.75, 1.5, and 2.0 mg/kg were given as a 10% aqueous solution; 0.38 mg/kg was given as crystalline cocaine HCl. Oral cocaine was administered in doses of 2.0 and 3.0 mg/kg. Intranasal cocaine kinetics were described by a 1-compartment open model with 2 consecutive first-order input steps and first-order elimination. Oral cocaine disposition was described by a 1-compartment open model with a lag time followed by a single first-order input phase and first-order elimination. The mean elimination half-life (t 1/2) for cocaine by the intranasal route to 7 subjects was 75 +/- 5 min (mean +/- SE). The mean t 1/2 after oral administration to 4 subjects was 48 +/- 3 min. The relative bioavailability [as determined by the area under the concentration-time curve (AUC)] for the 2.0-mg/kg dose by the intranasal and oral routes was not different. There was a linear increase in AUC with increasing intranasal dose.