GI Pharma Flashcards

1
Q

Steps of drug absorption

A

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

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2
Q

Why do you change disintigration of meds?

A

extend duration of effect (pharma)

improve compliance (take less pills)

improve patient satisfication (less peaks and troughs)

extend patent ($$)

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3
Q

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

A

lipid soluble drugs are MORE easily absorbed!!

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4
Q

first pass metabolism

A

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

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5
Q

p-glycoprotein

A

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

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6
Q

CYP34A

A

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

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7
Q

alcohol dehydrogenase

A

on surface of GI tract

men have more alcohol dehydrogenase at a younger age

men metabolize alcohol better than women

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8
Q

Why does sublingual bypass first pass metabolism?

A

mouth and anus are connected to systemic not portal!!

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

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9
Q

Why do antibiotics induce drug toxicity?

A

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

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10
Q

Why don’t we use Ipecac?m

A

20 min to vomit can be a long time now

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11
Q

stomach pumping

A

only removes toxins in stomach tht fit through holes

30% recovery

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

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12
Q

Activated charcoal

A

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

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13
Q

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

A

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

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14
Q

what is the role of P glycoprotein?

A

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

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15
Q

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

A

it increases it

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16
Q

Why do many oral abx alter digoxin pharmacokinetics?

A

some normal bacteria have the ability to metabolize digoxin

some abx interact w P-glycoproteins

17
Q
A