A new drug is found to be highly lipid soluble. It is metabolized at a slower rate of 10% per hour. On intravenous injection, it produces general anaesthesia that lasts only for 15 min. This short duration of anaesthesia is due to:
- Highly lipid soluble drugs get initially distributed to organs with high blood flow (Brain, heart, kidney etc). Later to less vascular tissues (muscle, fat). The plasma concentration falls and the drug is withdrawn from these sites. If the site of action was in one of the highly perfused organs, redistribution results in termination of drug action. Greater the lipid solubility of the drug, faster is its redistribution. This is seen in Thiopentone.
Metabolism of the drug in liver
High plasma protein binding of the drug
Excretion of drug by kidney
Redistribution