[redfox]

I have a graph to analyse which shows the amount of phenytoin in plasma over a
period of time.
I've said that the initial rapid decline was due to enzymes metabolising the drug but
after a while the enzymes (cyp450 I think) were in short supply so it wasn't metabolised
as rapidly. Does this sound as though it might be correct? I took a (semi) educated guess!

[Arkcon]

It would really depend on the shape of the graph, and any other hints they might have given you.  I can't be sure, but your explanation doesn't seem to me to be the best one for the phenomena I think you're describing.  I think.  Maybe.  (Good to toss a few extra of those words, in cases like this.)  Kinda.

[redfox]

Heh, ok...well basically the graph shows the concentration of drug in plasma rapidly decreasing at first then it decreases much more slowly over about 80 hours. There's not really a whole lot more to tell, but I'm just wondering why it would decrease so rapidly to begin with then what changes to make it decrease much less quickly...