Final answer:
The short action of thiopental is due to rapid redistribution from the CNS to other body tissues, reducing its concentration in the brain rapidly.
Step-by-step explanation:
The short action of thiopental is primarily due to rapid redistribution from the brain to other tissues after intravenous injection. This process quickly reduces the drug concentration in the central nervous system (CNS), leading to a decrease in its effects. Redistribution is a common characteristic of drugs that have a high lipid solubility, allowing them to cross the blood-brain barrier efficiently but also to disperse out of the CNS rapidly once the plasma levels decline.
While renal excretion and metabolism do play roles in the elimination of the drug from the body, these processes are not the primary reason for the drug's short action. Tolerance development and protein conjugation also do not account for the immediate short action following administration.