Absorption/Distribution Flashcards

1
Q

What is drug absorption?

A

Mass transfer process that involves movement of unchanged drug molecules from the site of absorption to the bloodstream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the rate limiting step for drug absorption?

A

Crossing the epithelia or endothelia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the rate of absorption related to?

A

Time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the rate of absorption measured by?

A

Time parameters (ka, tmax)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is ka?

A

Absorption rate constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is tmax?

A

time for the drug concentration to reach maximum in the plasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is absorption t1/2?

A

The time for 50% of the administrated dose is absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the extent of absorption related to?

A

Magnitude or amount of the drug reaching to systemic circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the extent of absorption measured?

A

Bioavailability (F) of the drug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the 4 factors influencing drug absorption from oral admin?

A

Type of dosage form
Physico-chemical properties of the drug
Physio-anatomic condition of the host patient
Pathologic conditions of the host patient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two main factors of physico-chemical properties of the drug

A

Aqueous solubility and permeability (log p)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the preferred route of administration?

A

oral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do lipids and proteins in the blood do for circulating concentration of the drug?

A

Serve to increase the circulating drug concentration for certain aqueous insoluble drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is permeability also dependent on?

A

pH (ionization)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What affects aqueous solubility and permeability?

A

Molecular weight
Ionization constant (pKa)
Solid state form
Particle size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are charged species restricted to during absorption?

A

Paracellular pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can drug release from the dosage form be affected by?

A

Excipients and manufacturing processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

For absorption to occur, drug molecules need to be in ____ at the absorption site

A

Solution

19
Q

Rank the rate of drug absorption from the oral dosage forms

A

Solutions
Emulsions
Suspensions
Capsules
Tablets
Coated Tablets
Enteric coated tablets
Sustained release tablets

20
Q

Drugs administered in ____ usually produce the most available drug product

A

Solution

21
Q

What is the most important physicochemical parameter for absorption of the drug

A

Solubility

22
Q

Low aqueous solubility results in ____ oral absorption

A

poor

23
Q

Solubility of weak acids and bases in aqueous medium is dependent on __

A

pH

24
Q

What happens when you decrease the particle size of a hydrophobic particle?

A

Surface area decreases
Need a surface active agent to increase effective surface area

25
Q

What is the rate of absorption of an ionizable drug predicted by?

A

The pKa of the drug and the pH of the absorption environment

26
Q

What must high lipid soluble drugs be accompanied by?

A

adequate water solubility

27
Q

Equation for permeability

A

Permeability = ((๐ท๐‘–๐‘“๐‘“๐‘ข๐‘ ๐‘–๐‘œ๐‘› ๐‘๐‘œ๐‘’๐‘“๐‘“๐‘–๐‘๐‘–๐‘’๐‘›๐‘ก) (๐‘ƒ๐‘Ž๐‘Ÿ๐‘ก๐‘–๐‘ก๐‘–๐‘œ๐‘› ๐‘๐‘œ๐‘’๐‘“๐‘“๐‘–๐‘๐‘–๐‘’๐‘›๐‘ก))/(๐‘€๐‘’๐‘š๐‘๐‘Ÿ๐‘Ž๐‘›๐‘’ ๐‘กโ„Ž๐‘–๐‘๐‘˜๐‘›๐‘’๐‘ ๐‘ ))

28
Q

What is stomach emptying?

A

It is the normal physiological process of the progression of the gastric contents toward the duodenum

29
Q

What can the rate of drug absorption be influenced by when talking about gastric emptying?

A

The rate at which the drug arrives at the small intestine

30
Q

What can gastric emptying rate be modified by?

A

Light physical activity - faster
Vigorous exercise delays it
Type, volume, viscosity, temperature of the ingested food (liquids eave the stomach faster than semisolids)
Concurrent drug therapy with cholinergic drugs increase the rate of gastric emptying

31
Q

What can limit the availability of drug molecules for absorption in the gut wall?

A

Enterocytes in the upper segment of the small intestine that express cytochrome P450 (CYP3A4)

32
Q

How can oxidation reactions mediated by CYP affect absorption?

A

Reactions involving the removal of various groups that make it less soluble

33
Q

Biliary salts example

A

They can interact with drugs such as neomycin and kanamycin to form insoluble and non-absorbable complexes

34
Q

What happens during drug secretion by efflux transporters in the GI?

A

after a drug penetrates the intestinal membrane and is in the cytoplasm of the enterocyte it may be subjected to secretion process mediated by a transporter which moves the drug back to the intestinal lumen

35
Q

What are the active carrier mediated efflux transporter proteins?

A

P-glycoprotein or multi drug resistance 1

36
Q

What does p-glycoprotein do?

A

limits drug absorption

37
Q

Where is p-glycoprotein expressed?

A

in the luminal membrane of the small intestine enterocytes

38
Q

How does drug degradation occur in the GI?

A

Gastric acid or several enzymes through enzyme mediated metabolism

39
Q

Examples of enzymes that degrade drugs?

A

lyases
hydrolases
proteases
glycosidases
sulfatases

40
Q

What is found more which decreases pH?

A

more bacteria

41
Q

Where in the GI tract are bacteria low in numbers?

A

The proximal part of the small intestine

42
Q

What pathologic conditions can change stomach emptying and GI permeability?

A

Celiac disease
constipation
diarrhea
vomiting

43
Q

What alterations of the GI causes changes in drug absorption?

A

Population of intestinal drug metabolizing enzymes
pH of the intestine
Normal GI flora (antibiotics)
Secretion of digestive enzymes
Intestinal blood flow (CV diseases)
Hepatic diseases ( liver cirrhosis)