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PK - Absorption
Pharm I - Block 1
16
Pharmacology
Not Applicable
05/17/2010

Additional Pharmacology Flashcards

 


 

Cards

Term
Passive diffusion
Definition

Is the movement of drug down the concentration
 gradient
It is an un-saturable process, does not require energy

Term
Facilitated diffusion
Definition

Drug movement is down the concentration gradient but requires a carrier. It is a saturable process

Term
Active Transport
Definition

Movement occurs against the concentration gradient and needs energy like ATP. It is a saturable process

Term
What important factors affect the absorption of a drug across a membrane?
Definition

Lipid solubility / Water solubility
•pH/ Nature of the drug?
The pH levels on either side of cell membrane
pKa of the drug

Term
Water soluble/ hydrophilic..
Definition
The ionised or electrically charged form of a drug and it …CANNOT cross membrane, thus it is fit for excretion.
Term
Lipid-soluble/ lipophiilic
Definition
 is the non ionised, or uncharged form….Can cross membrane, thus is fit for absorption.
Term
Decrease in pH
Definition

a weak acid will become more and more unionized, thus lipid soluble and better absorbed
a weak base  will become more and more ionized ,thus lipid insoluble,  and will not be absorbed. (Also becomes more water soluble and better excreted) .

Term
Increase in pH
Definition

a weak acid  will become more and more ionised,thus lipid insoluble and will not be absorbed. (Also becomes more water soluble and better excreted). 


a weak base will become more and more unionized , thus lipid soluble and better absorbed.

Term

Aspirin is an acidic drug. What will happen to it in the stomach and why.. what will be contraindicated when taking it?

 

Definition

Acidic drugs in acidic environments are unionised, thus lipid soluble and can cross membrane

For better absorption take on empty stomach… plus no antacid to be taken as this will decrease the acidity of the environment.

 

Term
pKa
Definition
is  equivalent  to the pH at which 50% drug is ionized and 50% is unionized
Term

In what circumstance would you need to acidify urine?

How can this be accomplished?

Definition

In basic drug poisoning (i.e  atropine & chloroquine), as this would make the base more ionised and better excreted.   
Give  Ammonium chloride or Vitamin C or Cranberry juice 

 

Term

In what circumstance would you need to make urine more alkali?

How can this be achieved?

 

Definition

in acidic drug poisoning (ie phenobarbitone), thus making it more ionised and better excreted.
Give  Sodium bicarbonate or Acetazolamide

 

Term
What are the barriers a drug must go through before it reaches circulation?
Definition

1. Broken down in intestine/ GI 

2. Some is excreated, other part travels though intestinal wall

3. Broken down in intestinal wall and sent via portal vein to liver

4. Broken down in liver.. then remaining part reaches systemic circulation

Term

What is Bioavaliability?

How is it calculated?

Definition

The fraction of the administered

dose reaching the systemic circulation in its chemically unchanged form. Designated as “ F ”

F = AUCoral / AUCiv

 

Term
What id First pass metabolism? Give an example if a drug which shows it and how this is overcome.
Definition

It is the fraction of lost drug during the process of absorption which is generally related to the liver and gut wall.

Lidocaine & nitrogylcerine shows this, and it is overcome by administering it through an IV (this route has 100% bioavaliability).

Term
What is Bioequivalence
Definition

Two different  brands (brand A and B) of a same drug give orally to the same person
If they differ in bioavailibility and rate of absorption …both brand A and B are said to be  Bioinequivalent…..this is common
If they have same bioavailibility and rate of absorption …both brand A and B are said to be  Bioequivalent…..this is uncommon

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