Reproducibility of saliva and plasma theophylline levels following single dose administration of two sustained release preparations.

1 Concomitant saliva and plasma theophylline concentrations were measured in six healthy male volunteers following single dose administration of two sustained release preparations (Nuelin SA and Phyllocontin Continus). 2 Using mean values, a good correlation was obtained between saliva and plasma drug concentrations. Prediction of plasma values using individual saliva was poor and varied widely. The ratio of saliva to plasma concentrations in the same individual, assessed under standardised conditions, was not always reproducible.