Will
concentration go higher?
One cannot tell from the two points given. It is possible that
the peak occurred earlier than the measured point and it is
possible that it may be later. However, noting that over the
entire dose interval, the change in concentration was small, it
is unlikely that a peak would be significantly higher, if this is
not the peak.
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Will concentration
go lower?
The simple answer is that the "trough" should be the
lowest concentration of the dose interval. If the drug were given
intravenously, there is no doubt about this statement. If the
drug is given orally, as is phenobarbital, then it is quitely
likely that the concentration will drop a bit more before a
significant amount of the drug is absorbed. Gastric emptying
time, dissolution rates, and other factors can contribute to
delayed absorption of drug.
However, in clinical pharmacokinetics, it is generally assumed that the trough represents the lowest and most reliable estimate of drug concentration.
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Is
the phenobarbital eliminated rapidly or slowly?
It is eliminated very slowly. In a "typical" animal, it
takes 53 hours for the concentration to decrease by half. The
concentration of most drugs we use in therapy will decrease by
half in much shorter time intervals. For example, the
concentration of penicillin G given intravenously will decrease
by half in less than one hour!
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EXPERIMENTAL SECTION! TEMPORARY
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