BLOOD AND SALIVA CLEARANCES OF PHENOBARBITONE AND PENTOBARBITONE IN HORSE

The clearance of phenobarbitone and pentobarbitone from blood and saliva has been studied in the horse. Although the concentration of each barbiturate was lower in the saliva than in the blood the clearance rates in both fluids were parallel, the concentration in the saliva being directly dependant on the non-plasma protein bound barbiturate. Following oral administration, phenobarbitone showed a non-logarithmic decline in blood concentration with time over the period of 0-6.5 hr. Pentobarbitone gave clearances of 46 per cent hr and 49 per cent per hr from blood and saliva respectively following i.v. injection. Following oral administration of each drug the maximum concentration in the saliva was reached in from 10 to 20 min. Plasma protein binding was 44 per cent for pentobarbitone and 15 per cent for phenobarbitone; only the latter was bound to saliva protein, to the extent of 7 per cent. © 1968.