Gastrointestinal absorption 2

Question 1

What type of compounds go through the efflux transporter p-glycoprotein?

Answer 1

lipophilic/ amphiphilic

Question 2

What type of transporter is the p-glycoprotein?

Answer 2

ATP dependent

Question 3

other than the intestinal epithelium where else is p glycoprotein expressed?

Answer 3

liver, brain, adrenal glands and kidney

Question 4

What is digoxin used for and how does it relate to p-glycoprotein?

Answer 4

heart failure and arrhythmias, substrate for p-glycoprotein

Question 5

How does rifampicin affect digoxin?

Answer 5

rifampicin is an inducer of p-glycoprotein therefore causes efflux from enterocyte to intestinal lumen

Question 6

How are macromolecules taken up?

Answer 6

endocytosis e.g. pinocytosis and phagocytosis

Question 7

Are colonic bacteria anaerobic or aerobic and what do they secrete to metabolise what?

Answer 7

anaerobic, secrete enzymes to metabolise endogenous and exogenous substances which escape digestion in upper GI

Question 8

What is the function of the colon?

Answer 8

absorption of water and electrolytes

Question 9

does the large intestines mucosa contain villi and microvilli

Answer 9

no villi but microvilli

Question 10

What is plicae semilunares?

Answer 10

irregular folds in large intestines

Question 11

Are the spectrum of metabolising enzymes different in the small intestines to the colon?

Answer 11

no both similar

Question 12

where are drugs absorbed from the colon and upper rectum absorbed into?

Answer 12

portal vein leads to 1st pass metabolism

Question 13

Do the drugs absorbed into lower rectum and anal canal experience first pass metabolism?

Answer 13

no

Question 14

What are the reasons of loss of oral bioavailability?

Answer 14

loss in faeces
decompose in lumen
destruction in wall of GIT
destruction in liver

Question 15

What is Lipinski’s rule?

Answer 15

empirical rule to evaluate drug likeness or if chemical compound can be an orally active drug

Question 16

What are the 4 rules of Lipinski?

Answer 16

not more than 5 H-bond donors
not more than 10 H-bond acceptors
molecular mass less than 500 Daltons
An octanol-water portion co-efficient (LogP) no greater than 5

Question 17

What are the 4 Biopharmaceutics Classification system (BCS) gradings?

Answer 17

class 1 - High solubility, high permeability 
class 2 - low solubility, high permeability 
class 3 - high sol, low perm 
class 4 - low sol, low perm