Lecture 30

Question 1

What are the mechanisms of drug permeation?

Answer 1

1. aqueous diffusion (paracellular)
2. lipid diffusion (trancellular)
3. special carriers
4. endo and exocytosis

Question 2

What is absorption when it comes to drugs?

Answer 2

transfer of a drug from its site of administration to the bloodstream

Question 3

What form is complete absorption or delivery

Answer 3

IV

Question 4

Explain the oral route of drugs

Answer 4

most convenient; absorption may be slower and less complete

suffers from first-pass effect (must go through gut wall and liver)

Question 5

What are the enteral routes of drugs?

Answer 5

sublingual- by pass first-pass effect

rectal - partial avoidance

Question 6

What are the paraenteral routes?

Answer 6

intravenous

intramuscular

subcutaneous

intradermal

Question 7

What are other routes of drug administration?

Answer 7

oral inhalation

nasal inhalation

topical

transdermal

Question 8

What factors influence drug absorption?

Answer 8

1. pH
2. surface area
3. blood flow to desired site
4. contact time
5. P-glycoprotein

Question 9

What are most drugs?

Answer 9

either weak acids or weak bases

Question 10

What is the effect pH has on drug absorption?

Answer 10

The protonated form of a weak acid is the more liposoluble form

The unprotonated form of a weak base is the more liposoluble form

Question 11

What kinds of drugs are excreted faster?

Answer 11

Weak acids are excreted faster in alkaline urine; weak bases are excreted faster in acidic urine.

Question 12

Where does most drug absorption occur?

Answer 12

the small intestine bc of the large surface area

Question 13

What is P-glycoprotein?

Answer 13

it is a transporter protein that is used to transport drugs across the cell membrane

reduces drug absorption

Question 14

what is bioavailability?

Answer 14

Fraction of administered dose of a drug that

reaches the systemic circulation

Question 15

how is bioavailability measured?

Answer 15

Bioavailability is determined comparing the AUC
after a particular route of administration with the
AUC after IV injection.

the area under the curve reflects the extent of absorption.

Question 16

What is drug distribution

Answer 16

It is the process by which a drug leaves the
blood stream and enters the extracellular fluid
and /or the cells of the tissues

Question 17

what affects drug distention?

Answer 17

blood flow

drug binding

capillary permeability

drug hydrophobicity

Question 18

What kinds of drugs can enter the CNS?

Answer 18

highly liposoluable or have an active transporter

Question 19

How does drug elimination occur?

Answer 19

metabolism and excretion

Question 20

How does metabolism lead to drug elimination?

Answer 20

many drugs are lipophilic and are not easily excreted

drugs are broken down into hydrophilic compounds which ends biological activity and elimination from the body.

Question 21

What enzymes are responsible for the metabolism of 80 percent of all drugs used?

Answer 21

cytochrome P450 system

Question 22

What drugs increases the synthesis of one or more P450 isoforms?

Answer 22

rifampin

phenobarbital

carbamazepine

Question 23

what are xenobiotic receptors?

Answer 23

They help regulate the transcriptional activation of genes

Question 24

What are the clinical consequences of enzyme induction?

Answer 24

A drug can increase its own metabolism

A drug can increase the metabolism of a coadministered drug.

This may reduce drug plasma concentrations below therapeutic levels

Question 25

What are drugs that inhibit cytochromes P450?

Answer 25

• Cimetidine
• Erythromycin
• Chloramphenicol
• Grapefruit juice

Question 26

What is the most common form of drug elimination?

Answer 26

renal excretion