Pharmacokinetics in dogs after oral administration of two different forms of ascorbic acid

The dog is able to synthesise ascorbic acid (AA), but is frequently given t he vitamin in an attempt to improve health and performance. Thc pharmacokin etics Of AA in this species, however, are not well studied. Using a selecti ve analytical method and careful stability control, the pharmacokinetics of orally given AA was studied in 20 dogs, at two dosage levels (15 and 50 mg kg(-1)) and with two forms of supplement [crystalline AA and the vitamin C product Ester-C (R) (Inter-Cal Corp., Prescott, AZ, USA)]. After oral admi nistration, a rapid increase was found in the plasma level Of AA, indicatin g a possible intestinal active transport mechanism in this species. The obt ained Cm,., and AUC values were found to increase in a non-linear fashion w hen the dose Of AA was increased. The pharmacokinetic modeling of the elimi nation Of AA was made difficult by a pronounced secondary peak appearing af ter about 9 hours. The comparison of crystalline AA and Ester-C (R) did not indicate any significant differences in pharmacokinetic parameters between the two preparations of the vitamin. (C) 2001 Harcourt Publishers Ltd.