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Husseinmr
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A woman needs a sleeping pill and we have two brands of diazepam. How do we
decide which one has faster onset of action?
I by comparing the two Tmax
I by comparing the rate of absorption
III by comparing two AUC
a. I only
b. III only
c. I and II
d. II and III
e. I, II and III
 

siteadmin
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Onset of action

Hmmmmm...

Well we don't know the therapeutic concentration of the drug which would be helpful, so I think, all three (option e) would be required. My reasoning:

Tmax is the time taken to reach maximum concentration. We would hope at maximum concentration the drug has been working for a while now, but we don't know when onset of action would of been by looking at Tmax.

The faster the rate of the absorption, you would think, would mean the faster the onset of action. But a drug could be rapidly absorbed but for many reasons not even reach a therapeutic concentration. So this indicator alone would not be a reliable way of measuring onset of action.

AUC will tell us the extent to which the drug that was administered was absorbed. In theory, the more extensive the absorption at an earlier time the more likely it is the drug will have a faster onset of action.

I think the combination of all three of these factors when compared between two drugs will be the most likely to give a fair comparison of the onset of action.

 

Mat :)

 

 

 

This is my an educated guess so I would like to hear what others have to say.