Value of saliva samples in monitoring carbamazepine concentrations in epileptic patients

Simultaneous saliva and serum concentrations of carbamazepine (CBZ) were determined by enzyme immunoassay technique (EMIT±) in 120 epileptic patients on long-term treatment with CBZ. Saliva specimens were collected after the patients had chewed paraffin for 5 min. The regression between serum and saliva concentrations of CBZ was linear. The correlation coefficient was 0.94 with a mean saliva/serum ratio of 0.31 (0.30–0.31, 95 % confidence limits). The serum/saliva correlation coefficients r = 0.92 and r = 0.95, as well as the mean saliva/serum ratios, 0.31 and 0.31, were comparable in 83 patients in CBZ monotherapy and 37 patients receiving additional drugs. The paraffin chewing facilitated the saliva sampling greatly, but resulted only in a minor increase of the serum/saliva correlation coefficient, 0.90 to 0.94, based on 45 patients on CBZ monotherapy where saliva was sampled just before as well as after paraffin chewing. The method of saliva sampling failed in five patients (4 %), but was otherwise applicable even in little children.

The findings indicate that the concentrations of CBZ in saliva instead of serum can be used to monitor CBZ treatment in epileptic patients, thus obviating the necessity of painful venipunctures.