COMPARATIVE PHARMACOKINETICS OF SULFAMETHAZINE IN PLASMA AND PAROTID-SALIVA OF SHEEP

Salivary output in sheep is large enough to be considered a physiologi c body fluid compartment. The hypothesis for this work was that pharma cokinetics of sulfamethazine in saliva was similar to that in plasma. A reliable technique was developed to measure parotid salivary output. Mean output of saliva was 3.18 +/- 1.04 L from a single parotid gland per day with a mean flow of 2.21 +/- 0.43 mL/min. Using concentration s of sulfamethazine in parotid saliva made it possible to calculate th e total passage of sulfamethazine to parotid saliva, which was calcula ted to be 3.5% of the total dose. Pharmacokinetic variables obtained f or sulfamethazine in plasma and in saliva were closely related (AUC 14 08 mu g.h/mL and AUC 1484 mu g.h/mL; Vd(area) 0.434 L/kg and Vd(area) 0.374 L/kg; t(1/2 beta) 4.30 h and 3.46 h, respectively) and no substa ntial differences were observed. The convenience of using salivary con centrations of sulfamethazine for drug monitoring is discussed.