need help in pharm ASAP - midterm tomorrow!!

[dr barb]

My prof's notes describe benzodiazepines as "highly bound to plasma proteins AND having a very large volume of distribution." Aren't these mutually exclusive? Doesn't being bound to plasma proteins mean that they mostly stay in the plasma compartment, and therefore would have a small volume of distribution. Or, if they do have a large volume of distribution, which I'm pretty sure they do, wouldn't be bound to proteins in the tissues? Are those also called plasma proteins?

Please help!

Thanks.

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[ckent]

Your prof was probably referring how benzo's penetrate the bbb. Are you sure that your prof didn't say that benzo's have a large bioavailability? They are readily absorbed, and bind to plasma proteins (different then interstitial proteins) and enter the bbb to act. Don't get too caught up with the concepts, just try to know the facts.

 

[dr barb]

thanks

 

[Samoa]

No, they are not mutually exclusive. A drug can be preferentially distributed to fatty tissues, leading to a large volume of distribution, and yet still be mostly bound to protein when in the plasma. Granted, the effects on measured plasma levels are in opposition to each other, but they are different characteristics, not opposing extremes of the same characteristic.