RESUMEN
Thiopentone and Ketamine were selected for this study since they are most frequently used as intravenous anaesthetics and could possess free radical production. 64 albino rats [200 gm +/- 10] have been administered an anaesthetic dose of the two drugs, control groups were treated similarly with saline. Blood and tissues samples were collected after 2, 12, 24 hours from administration of drugs. Determination of superoxide dismutase in blood, caeruloplasmin in plasma and cytochrome oxidase in liver and heart tissues revealed that: 1- Superoxide dismutase activity was significantly decreased after 2 hours following Ketamine and showed a highly significant decrease after 12 hours with thiopental and Ketamine and the activity returned to normal after 24 hours with both anaesthetics. 2- Caeruloplasmin level showed a significant decrease after 12 and 24 hours from Ketamine administration and only after 24 hours with thiopentone. 3- Cytochrome oxidase activity in liver tissue was decreased significantly 2 hours following thiopentone and after 12 and 24 hours following Ketamine administration. 4- Cytochrome oxidase activity in heart tissue showed no significant change at any time following administration of both drugs. It might be concluded from these results that the relation between thiopentone, Ketamine and the studied copper containing enzymes by production of free radicals during metabolism of both drugs. Thiopentone was less hazardous than Ketamine of given within 12 hours from the first exposure to anaesthesia