IV anaesthetics

[Blind date18]

Here was a question in u world stating that the drugs which are soluble in blood takes more time for their onset of action and even large amount of drug is required for induction,saying that PROPOFOL which is highly lipophilic drug has very rapid onset of action. considering above two statements together propofol will rapidly distribute itself into tissues ,so how can it have rapid onset?

inputs are highly appreciated ,thank you

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[chromuffin]

Here was a question in u world stating that the drugs which are soluble in blood takes more time for their onset of action and even large amount of drug is required for induction,saying that PROPOFOL which is highly lipophilic drug has very rapid onset of action. considering above two statements together propofol will rapidly distribute itself into tissues ,so how can it have rapid onset?

inputs are highly appreciated ,thank you

you already answered this and did not realize. Drugs which are highly soluble in blood take a long time for action to occur. Drugs which are highly lipophilic take less time for action to occur. Think of it this way. If a drug is lipophilic, it will not want to stay in your blood stream. Instead, it wants to get to your tissue. Conversely, drugs soluble in blood take a long time to leave the blood and go to tissue because it “likes the environment it is already in”. This is why propofol is quick acting.

 

[MrTaco92]

If you look at it in the context of lipophilicity, you could also consider that it would likely be easier for lipophilic anesthetics to cross the BBB, translating to quicker onset of action.