Diazepam and N‐desmethyldiazepam concentrations in saliva, plasma and CSF.

1 Salivary and plasma diazepam and nordiazepam concentrations were measured in 51 paired samples from four experimental situations. In seven of the patients CSF samples were estimated. 2 Correlation of 0.89 (P less than 0.001) was observed between salivary and plasma diazepam and 0.81 (P less than 0.001) between salivary and plasma nordiazepam. 3 Mean salivary diazepam was 1.6% (+/- 0.3%) of the plasma diazepam. It was found to vary markedly in an acute dosage study. Mean salivary nordiazepam was 2.9% (+/- 1%) of the plasma measure and was dependent on salivary flow rate. 4 CSF diazepam was in equilibrium with unbound plasma diazepam and salivary diazepam. 5 Mean protein binding of diazepam in vitro was 99.3% with no variations as a function of concentration. 6 The results suggest salivary diazepam and nordiazepam measures to be of value in epidemiological studies. However, they do not predict accurately the plasma total or unbound drug concentration from a salivary sample in an individual.