Chlordiazepoxide concentrations in saliva and plasma measured by radioimmunoassay

A new, sensitive and specific radioimmunoassay (RIA) for chlordiazepoxide was used to determine concentrations of the drug in microsamples of saliva and plasma obtained from subjects following intravenous and oral administration of the drug. Saliva and plasma concentrations of the drug were highly correlated (r = 0.95) and the saliva/plasma ratio had a mean value of about 0.03. Saliva levels of chlordiazepoxide were found to be equal to the concentration of unbound drug in the plasma. Drug half-lives determined from both plasma and saliva concentration-time curves were found to be equivalent.