The effect of L-tryptophan administration on the concentration of probenecid in plasma and cerebrospinal fluid in patients.

The administration of large doses of probenecid has been used to study the central nervous system metabolism of catecholamines and indoleamines in patients with affective disease. It has been reported that alterations of the binding of L-tryptophan to plasma albumin binding sites occur during probenecid administration. The present study sought to determine if the administration of large doses of L-tryptophan affected probenecid concentrations in cerebrospinal fluid and/or plasma. The data indicate that during L-tryptophan treatment, plasma probenecid concentrations are reduced but that no significant alterations in cerebrospinal fluid probenecid concentrations occur. This would suggest that the kinetics of the probenecid blockade of transport of acidic biogenic amine metabolites out of cerebrospinal fluid are not altered by L-tryptophan loading.