Pharmacokinetics (ADME)

Question 1

What is pharmacokinetics?

Answer 1

A branch of pharmacology that is concerned with movement of drugs within the body.

Question 2

What are the four stages of pharmacokinetics?

Answer 2

1. Absorption
2. Distribution
3. Metabolism
4. Excretion

Question 3

Where is the primary site for absorption?

Answer 3

Small Intestines

Question 4

How does Excretion occur?

Answer 4

Occurs via urine formed in the kidneys.

Question 5

Where is the principal site of drug metabolism?

Answer 5

The Liver

Question 6

Describe Absorption

Answer 6

• This is the process by which drugs (xenobiotics) enter the bloodstream.
• This can occur through passive diffusion, facilitated diffusion, active transport, or pinocytosis.

Question 7

What is the most common route of drug administration?

Answer 7

Orally

Question 8

What are advantages of Oral Administration?

Answer 8

• Self-administered
• Economical
• Pain-free

Question 9

What are disadvantages of oral administration?

Answer 9

• Variability in dose
• Effect too slow for emergencies
• First pass metabolism

Question 10

What are the advantages of Parenteral Administration?

Answer 10

• Can be used for medicines that are poorly absorbed

Question 11

What are the disadvantages of Parenteral administration?

Answer 11

• Can be costly, painful, and staff need additional training and equipment to administer.

Question 12

Define: Bioavailability

Answer 12

The amount of drug which is absorbed, relative to the amount administered

Question 13

What is the bioavailability of I.V. administered drugs?

Answer 13

100%

Question 14

What are the factors that affect bioavailability?

Answer 14

• Solubility
• Concentration
• Surface Area
• Blood Supply
• pH

Question 15

What is the order of drug administration?

Answer 15

Parenteral, oral, rectal, topical

Question 16

What is Distribution?

Answer 16

The transfer of a substance from one part of the body to another (blood to tissue)

Question 17

Highly ________ tissues receive ______ of the absorbed drug initially.

Answer 17

Perfused
Most

Question 18

_______ perfused tissues take longer to reach equilibrium with blood.

Answer 18

Less

Question 19

What are the factors that affect distribution?

Answer 19

1. Lipid Solubility
2. pH
3. Plasma protein binding

Question 20

What is the volume of distribution?

Answer 20

Quantifies the distribution of a drug (xenobiotic) between plasma and the rest of the body.

Question 21

What is the equation to calculate volume of distribution (L)

Answer 21

Volume of distribution (L) = amount of drug (mg) / concentration (mg/L)

Question 22

What does a small Vd value mean?

Answer 22

The drug distributes mainly into central compartments

Question 23

What does a large Vd value mean?

Answer 23

The drug distributes more widely in the body.

Question 24

What is Metabolism?

Answer 24

Metabolism is the enzymatic process by which the structure of a drug (xenobiotic) is altered to convert the drug into a more water soluble compound in order to facilitate removal from the body.

Question 25

What is First Pass Metabolism?

Answer 25

First-pass metabolism is the intestinal and hepatic degradation of a xenobiotic taken by mouth, after absorption. This results in a significant reduction in the concentration of unmetabolised drug reaching the systemic circulation, so it reduces the bioavailability of the drug.

Question 26

How many phases of metabolism are there?

Answer 26

Phase I - Modification Phase II - Conjugation Phase III - Transport

Question 27

Describe Phase I (modification) of Metabolism

Answer 27

Phase I biotransformation reactions introduce, or expose, functional groups on the drug with the goal of increasing the polarity of the compound so it can be effectively eliminated by the kidneys. Cytochrome P450 enzymes are responsible for most phase I reactions. Most phase I enzymes are located in the endoplasmic reticulum of the liver.

Question 28

What are the 3 reaction categories of Phase I

Answer 28

Oxidation Reduction Hydrolysis

Question 29

What is Cytochrome P450?

Answer 29

Is primarily found in lover cells and accounts for 70 to 80% of enzymes involved in drug metabolism.

Question 30

How do you name Cytochrome P450

Answer 30

Each cytochrome P450 gene is named with CYP. 1. A number within the gene family 2. A letter representing gene subfamily 3. A number assigned to a gene within the subfamily.

Question 31

Describe Phase II (conjugation) of metabolism

Answer 31

- Takes place if phase I is insufficient to clear a compound from circulation, or if phase I generates a reactive metabolite - Involves adding a large polar group to further increase the compound’s solubility - Transferase enzymes are responsible for most phase II reactions

Question 32

Describe Phase III (Transport) of Metabolism

Answer 32

- Involve drug transporters, which influence the effect, absorption, distribution and elimination of a drug - Drug transporters move drugs across cellular barriers - They are located in epithelial and endothelial cells of the liver, gastrointestinal tract, kidney, blood-brain barrier and other organs

Question 33

What is Excretion?

Answer 33

The final removal of drugs (xenobiotics) or their by-products from the body. Also referred to as elimination

Question 34

What are the main excretory organs?

Answer 34

The kidneys

Question 35

What are some elimination pathways?

Answer 35

Urine, tears, saliva, bile, respiration, perspiration, faeces, milk.

Question 36

Define: Half life

Answer 36

The time required to eliminate half (50%) of the absorbed dose of a drug from an organism

Question 37

What is the half-life for paracetamol, morphine, and codeine?

Answer 37

Paracetamol - 1 to 3 hours Morphine - 2 to 3 hours Codeine - 3 to 4 hours