Pharmacokinetic study of ascorbic acid in sheep

Four groups of sheep (5/group) were used in the experiment. Group 1 sheep were given 1 g of ascorbic acid (AA) intravenously (i.v.), group 2 were given 3 g i.v., group 3 were given 1 g intramuscularly (i.m.) and group 4 received 3 g i.m. Blood was collected for 7 h after i.v. administration and for 48 h following i.m. administration. Plasma was analyzed for AA using HPLC techniques. After i.v. administration the rate of elimination was greater at the high dose than the low (0.8560 vs 0.5231 h-1) but the area under the curve (AUC) parameter was proportional to the dosage (127.9 vs 39.7 mcg*h/mL). After i.m. administration AUC parameters were higher than following the i.v. injections. When the times that AA levels were > or = 5 mcg/mL after i.m. injection were compared there was no significant difference between the 1 and 3 g dosages. Times that levels were > or = 10 mcg/mL were significantly longer for the 3 g dose. Using the AUC (area under the curve) parameter as an index of drug exposure, supplementation of adult sheep with AA by the i.m. route should have a greater effect on the animal than i.v. administration.