Distribution - Tricia V

Question 1

What is distribution and how does it occur?

Answer 1

Drug distribution is the process of drugs moving throughout the body. It can occur through passive diffusion or active transport through the bloodstream.

Question 2

What qualities of drugs influence their transport?

Answer 2

size, charge, and chemical structure

Question 3

Passive diffusion can occur under what conditions?

Answer 3

Diffusion may be able to occur if the drug is small, uncharged, unbound (ex plasma proteins) and has the right balance between water and lipid solubility AND there is an appropriate pH for the drug to maintain its structure

Question 4

T/F pH can alter a drugs charge/ionization

Answer 4

True

Question 5

What size molecules are the best candidates for diffusion?

Answer 5

Molecules with a molecular weight of 500 (g/mol?) or less.

Question 6

What is the equation for pH

Answer 6

pH= -log[H+]

Question 7

Each 1 unit of pH change leads to what degree of concentration change?

Answer 7

Each 1 unit of pH change represents a 10-fold increase or decrease in the concentration of hydrogen ions,

Question 8

What is pKa?

Answer 8

pKa = the pH at which the drug (or biochemical functional group(s) ) exists half in the charged state and half in the uncharged state is defined as its acid dissociation constant.

Question 9

T/F pKa is a fixed property for each individual drug

Answer 9

True. We can calculate the percentage of charged and uncharged molecules for a drug at any pH if we know its pKa.

Question 10

What is ion-trapping

Answer 10

Passive diffusion proceeds until the concentration of un-ionized drug is the same on both sides. As a result, pH differences can cause more drug to accumulate based on the fraction of un-ionized and ionized molecules.

Question 11

Where are plasma proteins produced and what does their presence reflect?

Answer 11

plasma proteins are produced in the liver, and their presence in the blood reflects liver function, nutritional status, and the effect of aging and disease.

Question 12

What are some examples of plasma proteins

Answer 12

Albumin, lipoproteins, sex-hormone binding globulin, alpha-1-acid glycoprotein

Question 13

What is the role of plasma proteins regarding drug distribution?

Answer 13

Plasma proteins circulate freely in the bloodstream helping distribute drugs bound to them. While bound, drugs are protected from metabolism and excretion, extending the time the drug remains in the body.

Question 14

T/F drugs can only have their effect after they are unbound from the plasma protein

Answer 14

true. must unbind to act on a receptor

Question 15

What is volume distribution

Answer 15

a hypothetical value that reflects the volume in which a drug would need to be dissolved to explain the relationship between dosage and blood levels.
ex: If we administer a dose of 100 mg and the plasma concentration is 2 mg/L, then it appears the drug is distributed in 50 L.
If we administer the same dose and the plasma concentration is 20 mg/L, then it appears as though the drug is distributed in a volume of 5 L