first pass metabolism in liver versus bioavailability

[Patricia Kelly]

Hi guys

Which are the administration routes that are not influenced by first pass metabolism?

ONLY : INTRAVENOUS, INHALATION AND TRANSDERMAL

Oral, intramuscular and subcutaneously are influenced.

The Bioavailability factor (F) can give us an idea of how is affected the bioavailability by a first pass metabolism in liver

If we consider that F is a "fraction", the greater the fraction, the greater the bioavailability of the NON-VIV administration route.

Does it makes sense?


The non-viv could be oral route, intramuscl, subcut.
If we want to know the Fraction, just divide AUC of the non-viv drug and the AUC of the VIV drug

F=AUC vo /AUC VIV

[Ohm]

Hi kelly I have a doubt about this, IV line is 100% bioavailble But I think all the parentral routes , sublingul , rectal, and vaginal are exempt from first pass effect. and I guess transdermal too. Please let me know if I am right.

The formula what you gave is the right, that is helpful in how much drug is availabe from that very route comparing to compared to IV especially useful in comparing different routes with IV

[mitocondria]

I think IV, IM, SC, SL, IR, I. Vaginal, TD, Inhalation all avoid first pass metabolism, only oral route has First pass metabolism

Pl. correct if I am missing something

Hi kelly I have a doubt about this, IV line is 100% bioavailble But I think all the parentral routes , sublingul , rectal, and vaginal are exempt from first pass effect. and I guess transdermal too. Please let me know if I am right.

The formula what you gave is the right, that is helpful in how much drug is availabe from that very route comparing to compared to IV especially useful in comparing different routes with IV

[Patricia Kelly]

according to appleton, intramuscular and subcutaneous undergo first pass metab
please keep checking
i will look another book

[jak073]

some of the topical routes like IM, SQ, inhallation undergo a second pass ia the lungs ......therefore they do not go thru first pass via the liver i think only the oral route does.....

others that avoid FPE" buccal, rectal, vaginal