We studied the pharmacokinetics of the glutamate antagonist NBQX (6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione) in 16 normal male volunteers aged 18--37 years in a double-blind, placebo-controlled design. Intravenous infusions of 0.0075 and 0.03 mg kg(minus sign1) over 30 min were given to six subjects at each dose level (parallel groups). Two subjects at each dose level received placebo. The drug was well tolerated and no clinically significant alterations of cardivascular or renal function or in biochemical and hematological parameters were observed. Mean values of C(max) were 41 and 177 ng ml(minus sign1) at the two-dose levels. Compartmental pharmacokinetic analysis yielded a plasma half-life of 0.75 h, a total plasma clearance of 0.222 L h(minus sign1) kg(minus sign1) and a volume of distribution at steady state of 0.153 L kg(minus sign1). The renal clearance was 0.130 L h(minus sign1) kg(minus sign1) implying tubular secretion of the drug.