fe and fu

not sure wether this sounds sensible..

is there any relationship between fraction excreted unchanged and fraction unbound?

If I'm not mistaken, there should be a link between fu and fe.
I think it can be seen by the renal clearance formula.

Besides, I think e.g when fu is large there is more drug likely to be excreted since this means the drug is often free to be filtered or polar and bound drugs tend to be more lipophilic. But this doesn't mean that bound drugs cannot be excreted, if conditions such as high urine flow etc., the bound drugs is still likely to be secreted.

Correct me if I'm wrong.

quite weird.i'm not sure whether this is pure coincidence,but i found in P n B parctise test (past years) that fe is inversely proportional to fu...

so,can anyone explain this, as well as (maybe) by using mathemathical approach of their relationship? that is,if there is any..

(i'm sure they're not cousins.LOL...it's meant to be a joke.not sure if it's funny)

Tq..

Hmmmm.... I don't think there's a direct relationship between fe and fu.

fu is basically influenced by binding to plasma proteins.
fe, on the other hand, is pretty much dependent on whether a drug is eliminated by hepatic metabolism or renal clearance.

They might be linked to the properties of the drug, ie whether the drug is polar, but I think the similarities end there.

But it'll be nice if someone can show how the two variables are mathematically related though =)

Since fe= CLR/CL and CLR = (fuGFR + (QR.fu.CLi)/(QR + fu.CLi))(1-FR)
wouldn't those two be linked when we replace CLR.. sorry to complicated to type it out..heheh