Inhaled Anesthetic Potency

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bbpiano1

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There is a UW question along the lines of "Which of the following values would you use to determine if a new anesthetic is high potency?"

A. Blood:lipid partition coeff
B. Minimal alv conc

The correct answer is B, but isn't A also right? FA states that drugs with high lipid solubility have high potency (pg 396).

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actually both are measures of potency.

But the question is referring to a "new drug". and for new drugs, you specifically use MAC to determine how much of a dose would produce anesthesia in 50% of the test subjects.
 
lipid solubility can be used to determine the potency, but MAC is the most direct route for comparison of potency as it is the definition of potency.
 
lipid solubility can be used to determine the potency, but MAC is the most direct route for comparison of potency as it is the definition of potency.

Yep.. Agree MAC is the way to go.

Also, lipid solubility though it gets more drug in, it doesn't necessary react right away and with strong affect either. You can have a very lipid drug but not a very reactive one. But when you compare to equal drug and ask which is more potent, the one that is more lipolic will typically have greater affect because more of it penetrate unless you have "bombardment effect".

Bottom line: It's all about the MAC :laugh:
 
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Just did this question: I agree that MAC is the answer, but my understanding of blood:lipid coefficient is that this is used more in terms of measuring speed of induction and recovery than potency per se. For example, Nitrous has a very low potency, but since it has a high blood:lipid coeff, it has a rapid onset and recovery. Halothane is the opposite, high potency (low MAC), but a low blood lipid coeff so a slow onset and slow recovery.
 
Just did this question: I agree that MAC is the answer, but my understanding of blood:lipid coefficient is that this is used more in terms of measuring speed of induction and recovery than potency per se. For example, Nitrous has a very low potency, but since it has a high blood:lipid coeff, it has a rapid onset and recovery. Halothane is the opposite, high potency (low MAC), but a low blood lipid coeff so a slow onset and slow recovery.
Speed of onset has to do with blood:gas coefficient, while potency has to do with blood:lipid coefficient. I am sure there is some correlation between the two though.
 
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