Zack PharMa

Question 1

Mechanisms of drug absorption?

Answer 1

1) simple passive diffusion- small hydrophobic drugs
2) facilitated diffusion
3) active transport
4) endocytosis

Question 2

Most weak acid drugs are absorbed at what site of GI tract

Answer 2

Proximal duodenum or the gastro duodenal junction.

Question 3

Weak bases are best absorbed at what part of the GI tract ?

Answer 3

Distal duodenum

Question 4

In shock drugs administered IV: Why?

Answer 4

It is because the blood flow overall and in particular into the GI tract are reduced in shock. Therefore, drugs administered PO will not be absorbed adequately

Question 5

What are the factors affecting drugs absorption?

Answer 5

1) Ph of the site of drug absorption.
2) blood flow
3) Total surface area and contact time available for the drug.
4) P glycoproteins ( seen in some people)which cause exocytosis of the drug back into the GI tract. It is one of the causes of multidrug resistance.

Question 6

The formula for bioavailability is ?

Answer 6

F= AUC oral / AUC IV
F= bioavailability
AUC = area under the curve

Question 7

Factors affecting bioavailability?

Answer 7

1) The solubility of the drug: The more hydrophobic and the smaller the drug, the more bioavailable it is.
2) instability of the drug: the drugs that are susceptible to degradation by GI PH or GI enzymes, if given orally will have poor bioavailability
3) First pass effect

Question 8

For the best absorption of a weak base drug, the PH should be?

Answer 8

Very close to the Pka of the drug

Question 9

Basic drugs are bound to what in plasma protein?

Answer 9

Alpha-01 acid glycoproteins