pharmacokinetic question help please

[nikei3ball]

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i'm confused.... say a drug has low bioavailability (i.e. propranolol with F= 10%). if someone has liver disease where there is a decreased first-pass effect, does that mean an increase in bioavailability and increase effect in the drug?

 

[Aznfarmerboi]

possibly in the sense that since the liver isnt working as well, more drug get through without being metabolized. On the other hand, if it is the metabolites that are active, then the bioavaibility might decrease for the active drug.

 

[patmcd]

It would depend on what the function of the 1st pass metabolism is on the drug. If its only elmination, then bioaval would increase. But if the drug requires metabolism in the liver for activation, then bioaval would go down.

 

[RX CARE]

i'm confused.... say a drug has low bioavailability (i.e. propranolol with F= 10%). if someone has liver disease where there is a decreased first-pass effect, does that mean an increase in bioavailability and increase effect in the drug?

Propanolol, specifically is a prodrug. So without first pass, it will not lead to its active metabolite. So I guess there will be decreased bioavailability and therapeutic effect.

 

[louisvalerie]

I think the bioavailability would increase in this situation. Propanolol is the drug which has high first-pass effect, so the bioavailability when we use this drug orally is low. If the patient has liver disease, the bioavailabily and the toxicity would increase b'cause the first-pass effect decreases. I'm not sure 'bout the prodrug,RX CARE! But I think when people say propanolol has high first-pass effect but low bioavailability, it could hardly be a prodrug. Just give you guys some of my ideas, can anyone explain it more?