EFFECTS OF PHENOBARBITAL ADMINISTRATION ON RESULTS OF SERUM BIOCHEMICAL ANALYSES AND ADRENOCORTICAL FUNCTION-TESTS IN EPILEPTIC DOGS

Objective-To determine what effects long-term phenobarbital administra tion to dogs with epilepsy would have on serum biochemical factors and adrenocortical function. Design-Prospective, uncontrolled study. Anim als-Five dogs with idiopathic epilepsy. Procedure-Serum total protein, albumin, total bilirubin, and cholesterol concentrations and serum al kaline phosphatase and alanine aminotransferase activities were measur ed before and 2 weeks, 6 months, and 12 months after initiation of phe nobarbital administration. Endogenous ACTH concentration was measured, and ACTH stimulation and low-dose dexamethasone suppression tests wer e performed at the same time. Results-Serum albumin concentration decr eased in 4 of 5 dogs, and serum cholesterol concentrations decreased i n all 5 dogs over the course of the study. Serum alkaline phosphatase concentration and alanine aminotransferase activities increased over t ime, and were greater than the upper reference limits in 4 of the 5 do gs by the end of the study. Endogenous ACTH concentration increased in all dogs but remained within reference limits. Plasma ACTH-stimulated aldosterone concentration increased over the course of the study. Pla sma cortisol concentration did not suppress, after administration of d examethasone, in 1 dog after 6 and 12 months of phenobarbital administ ration. Clinical Implications-Although endogenous ACTH concentration s hould be normal in dogs receiving phenobarbital, results of ACTH stimu lation and dexamethasone suppression tests may be altered. Serum album in and cholesterol concentrations, and serum alkaline phosphatase and alanine aminotransferase activities may also be abnormal.