Abstract
In order to investigate the predictability of theophylline concentrations in plasma from those in saliva, the total concentration (bound plus free) in plasma (Pt) and the free (unbound) concentration (Pf) were compared with the concentration in saliva (S), respectively.
Ten healthy males and three females were orally administrated a sustained-release theophylline preparation (Theo-Durr®) by a single dose of 8.13mg/kg and then, as the second experiment, six out of the above thirteen volunteers were administrated 400mg of theophylline daily for five days.
In the experiment of the single dose, there was no significant difference in the elimination half-life of theophylline between plasma and saliva.And both the ratios of S/Pt and S/Pf were 0.61, 1.60, respectively, up to 24 hours of dosing.In the case of multiple dose administration, 33.3 and 61.1% of the predicted Pt and Pf values which were calculated from the S/Pt and S/Pf for each volunteer coincided with the measured values within the deviation of ±10%, respectively. Moreover, S/Pt and S/Pf in the second experiment made a great change in comparison with them in the experiment of the single dose.From these results it was concluded that the use of saliva to predict theophylline concentrations in plasma has an substantial error and may lead to incorrect dosage adjustments.
