Comparison of plasma and saliva levels of diazepam.

1. Salivary, unbound and total plasma levels of diazepam have been compared in nineteen subjects. 2. Salivary diazepam levels were significantly higher (P < 0.001) than, but closely related to the corresponding unbound levels (r = 0.97) at 2.5-3 h after administration of the drug. 3. The results presented suggest that saliva levels can be used to predict the corresponding plasma levels at a given time, but there is no 1:1 relation between the unbound diazepam concentration in plasma and the saliva level of the drug.