AUC=f·D/CL [Study As­sess­ment]

posted by Helmut Homepage – Vienna, Austria, 2018-02-08 11:28 (1944 d 03:08 ago) – Posting: # 18379
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Hi sussu,

❝ I thought the AUC would be effect because I saw the the black area in the below picture. Now i know the AUC is only depend on the dose as you said.

❝ [image]

Exactly. The input function does not appear in the basic equation of PK (AUC=ƒ·D/CL). Since after an i.v. dose ƒ=1 (by definition) and the entire dose was administered, the AUC will be exactly the same regardless the input scheme.
Say you stopped after 15 minutes and administered the remaing dose after 29 minutes as a fast (one minute) bolus, it will look like this:


Note that the red line after tmax is above the blue one. With a t½ of 8 h the “missing” part before tmax will be outweighed in the elimination phase (speaking of AUC0–∞; the AUC0–2 will be lower, of course).

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