Bioavailabilities of carbamazepine (CBZ) tablets were studied by using saliva and serum levels in five healthy volunteers. Three commercial tablets (A, B, and C) and a solution containing 200mg of CBZ were administered orally. The CBZ levels in saliva and serum were determined with high-performance liquid chromatography.
The CBZ levels in saliva were extremely high during 2h after administration in the volunteers receiving a solution of CBZ and in a volunteer who has a habit of crunching after administration of tablets, as it is considered that the effect of the drug remaining in the mouth appeared.
There was a linear correlation between saliva and serum levels of CBZ in four volun-teers who did not crunch the tablets (γ=0.85, p<0.05) . The saliva and serum levels of CBZ were in the order of tablet A, B, and C at 1 and 2 h after administration.
There was a statistically significant difference between tablet A and B or tablet A and C in the serum levels at 1 h. However, there was little difference in saliva levels among tablet A, B, and C. It was observed that the AUC of saliva and serum was little different among tablet A, B, and C. The ratio of AUC of saliva to that of serum was 0.266±0.056 (S.D.) .
From these results, it should be considered that the bioavailability of CBZ tablets is assessed by the use of saliva levels instead of serum levels.