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Flashcards in GI Pharma Deck (17):

Steps of drug absorption

1. disintegration

slowed by product formation such as sustained release, enteric coating

2. dissolution

slowed by acidic pH for weak acids, water insolubility, large particle size

3, absorption

slowed by decreased gastric emptying, increased ionized drug, fast SB transit time

4. first pass metabolism 

enzyme saturation, P450 or PGP inhibitors result in less first pass metabilis and increased bioavailability

5. distribution


Why do you change disintigration of meds? 

extend duration of effect (pharma) 

improve compliance (take less pills)

improve patient satisfication (less peaks and troughs) 

extend patent ($$)


Does lipid solubility increase or decrease how well a drug is absorbed from the gut? 

lipid soluble drugs are MORE easily absorbed!!


first pass metabolism

pre-systemic - changes that occur before drugs reach the systemic circulation

drug modification

enzymes on gut lumen (metabolism before enters portal blood) 

enzymes in the liver (metabolism before enters IVC)


first in enterocytes then hepatocytes

from the moment it enters the gut until it enters systemic 

absorb in SB - go to portal circulation and liver - some kicked out - amt that goes to heart + systemic circulation



orignially identified because of its role in the development of multidrug resistance during chemo 

efflux transported located in the plasma membrane which translocates its substrates from the inside of the cells to the ouside 

"flipase" , extruder 

kick things out or prevent them from getting in

everywhere on protected surfaces - brain, gut, testes, ovaries - kick things out and prevent them from getting in 



associated with P glycoproteins - kick things back into gut lumen - anywhere in the body 


alcohol dehydrogenase 

on surface of GI tract 

men have more alcohol dehydrogenase at a younger age 

men metabolize alcohol better than women


Why does sublingual bypass first pass metabolism? 

mouth and anus are connected to systemic not portal!! 

i.e. nitroglycerin has a high first pass!! 


Why do antibiotics induce drug toxicity?

bacteria in the microbime can degrade drugs

antibiotics can cause toxicity because if you get rid of them less is metabolized in gut and you have toxicity 

i.e. Digoxin


Why don't we use Ipecac?m

20 min to vomit can be a long time now


stomach pumping

only removes toxins in stomach tht fit through holes 

30% recovery 

a lot of complications! respiratory depression, increased vagal tone, aspiration, trauma 


Activated charcoal

things stick in large SA 

don't get into body and enhances elimination 

adsorbs many toxins - prevents absorption and enhances elimination (enteroenteric and enterohepatic) 

2x more effective than lavage

need high charcoal:drug ratio! 

passive diffusion - how pill gets through - reverse concentration gradient and drag drugs OUT 


How do you get out drugs that are too small or not charged right for charcoal or lavage? 

golytely - stool aggressively 

forceful diarrhea to pull out

fluid and electrolytes!

huge molecule holds water in the gut and has electrolytes so you don't lose a ton 

decreased GI transit time

not associated w any clinically significant fluid or electrolyte alteriates


what is the role of P glycoprotein? 

prevents access of certain drugs from getting into the blood from the gut 


Increasing the lipid solubility of a drug has what effect on it's absorption from the GI tract? 

it increases it


Why do many oral abx alter digoxin pharmacokinetics? 

some normal bacteria have the ability to metabolize digoxin 

some abx interact w P-glycoproteins