Sustained blood concentration of salicylic acid following rectal administration of salicyluric acid in dogs.

ABSTRACT

The blood concentrations of salicyluric acid and salicylic acid following rectal, intravenous and oral administrations of salicyluric acid (5, 10 and 60 mg/kg, respectively salicylic acid equivalent) were determined in dogs. After rectal administration, a small amount of salicyluric acid was absorbed in intact form. The rest was hydrolyzed to salicylic acid, which was subsequently absorbed. The blood concentration of salicylic acid was maintained at 0.4-0.7 microgram/ml from 2 to 12 h. Following intravenous administration of salicyluric acid, salicyluric acid was detected in the blood but was rapidly eliminated. A trace amount of salicylic acid was detected, suggesting that systemic de-conjugation of glycine was involved. After oral administration of salicyluric acid, salicyluric acid was well absorbed. Salicylic acid was detected at low concentration for 12 h. Species difference in the metabolic fate of salicyluric acid in dogs, rabbits, rats and humans reported previously is discussed.