Ontogenic drug studies in calves. I. Age dependent salicylate levels and metabolism.

Acetylsalicylic acid (ASA) was administered to 52 Friesian calves 1--60 days old by oral route in the field, 63.5 mg/kg body weight constantly between 9 and 10 a.m., i.e., 3--4 h after morning feeding. The animals were divided according to age into groups. Total salicylate levels, salicylic acid and salicyluric acid plasma levels were determined up to 6 h after administration. The older the animals, the lower were the total salicylate and salicylic acid levels and the higher the salicyluric acid levels. The age dependence is highly significant during the first two weeks of life. Glucuronides could not be detected in quantitatively measurable amounts.