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 the vitamin in an attempt to improve health and performance. The pharmacokinetics of AA in this species, however, are not well studied. Using a selective 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(Inter-Cal Corp., Prescott, AZ, USA)]. After oral administration, a rapid increase was found in the plasma level of AA, indicating a possible intestinal active transport mechanism in this species. The obtained C(max)and AUC values were found to increase in a non-linear fashion when the dose of AA was increased. The pharmacokinetic modeling of the elimination of AA was made difficult by a pronounced secondary peak appearing after about 9 hours. The comparison of crystalline AA and Ester-C did not indicate any significant differences in pharmacokinetic parameters between the two preparations of the vitamin.