Pharmacology

Question 1

What does ADME stand for in pharmacokinetics?

Answer 1

Absorption, Distribution, Metabolism, Excretion

Question 2

Define the word pharmacokinetics.

Answer 2

What the body does to a drug (how does it respond and how does the drug move through the body).

Question 3

Define the word pharmacodynamics.

Answer 3

What a drug does to the body (the biological responses/reactions that occur from the body, because of the drug).

Question 4

Describe the process “First Pass Metabolism”

Answer 4

Following oral administration, a drug gets metabolised at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation.

Question 5

List 4 organs where first pass metabolism takes place.

Answer 5

Liver, lung, intestinal lumen, intestinal wall

Question 6

Briefly outline the meaning of the term ‘bioavailability’.

Answer 6

How much of a concentration of an active drug is left, once it has entered systemic circulation.

Question 7

List the 4 main routes of drug administration.

Answer 7

Oral, rectal, injection, topical, (buccal)

Question 8

What are the pros and cons associated with oral route drug administration?

Answer 8

PROS: low infection risk, very simple/self administration.
CONS: harsh environment (stomach), first pass metabolism (reducing bioavailability).

Question 9

What are the pros and cons associated with topical route administration?

Answer 9

PROS: Local effects, low systemic effects, limited first pass metabolism, suited to slow, continuous administration, usually low infection risk.
CONS: risk of systemic absorption (direct to blood), drug must be lipid soluble, small in molecular size and use a carrier molecule (process of lipid permeation).

Question 10

What are the pros and cons associated with injection route administration?

Answer 10

PROS: rapid bioavailability for intravascular, avoids first pass metabolism.
CONS: infections risks, targeting risks.

Question 11

List the 5 types of injections and briefly describe where the drug enters.

Answer 11

Intravascular (IV/IA) - directly into bloodstream
Intramuscular (IM) - into skeletal muscle
Subcutaneous (SC) - absorbed from subcutaneous tissue
Dermal (ID) - dermal vascular layer
Depot injection - for slow release formulations

Question 12

What is the difference between an enteral route and a parenteral route of drug administration?

Answer 12

The main difference is that an enteral route is via the gut, so uses the digestive system (mouth, stomach, small intestine) whereas a parenteral route completely bypasses the gut and digestive system.

Question 13

What are the main processes that affect drug absorption?

Answer 13

Aqueous diffusion, Passive diffusion, carrier-mediated diffusion and active transport.

Question 14

Define absorption and outline 2 factors affecting it.

Answer 14

The journey of a drug travelling from the site of administration to the site of action/systemic circulation.

Route of administration and permeation (the process)
(Drugs must be in solution to be absorbed)

Question 15

Define distribution and outline 3 factors that affect it.

Answer 15

The disbursement of an non-metabolised drug as it moves through the body’s blood and tissues.

Protein binding - only fractions of drugs not bound to plasma protein can cross membranes and bind to receptors.
Blood flow - to different parts of the body is very different (tissue perfusion rate).
Membrane permeation/tissue solubility - Fick’s Law.

Question 16

List the important properties of Fick’s Law, relating to drug absorption.

Answer 16

Membrane is proportional to surface area.
Permeability constant - the rate at which the drug can move across a membrane.
The concentration gradient between two areas.
The thickness of the exchange surface.

Question 17

Describe the process of phase one metabolism.

Answer 17

Oxidation - cytochrome P450 enzymes primarily found in the liver and help with chemical reactions that change:

1. Polarisation of the substance (making it charged)
2. Increase water solubility
3. Reduce pharmacological activity (but can activate prodrugs)

Question 18

Describe the process of phase two metabolism.

Answer 18

Conjugation - converting the drug/toxin by covalently joining them to other molecules/endogenous substances which:

1. Makes it water soluble
2. Biologically inactive

Question 19

Define the term ‘drug half-life’.

Answer 19

The time taken to decrease plasma concentration of an active drug to/by 50%.

Question 20

Name the four types of protein targets for drugs to bind to.

Answer 20

Enzymes, receptors, ion channels, carrier molecules.

Question 21

Describe the process of pro-drug conversion using codeine as an example.

Answer 21

Codeine is a pro-drug meaning it must undergo chemical conversion by metabolic processes before becoming an active, therapeutic agent. Using the enzyme Cytochrome P450 2D6 in the liver, codeine is converted into morphine to become a much stronger activator (active drug).

Question 22

Briefly describe the difference between an ion channel blocker and an allosteric modulator.

Answer 22

An ion channel blocker physically blocks the pore/active site to inhibit movement whereas an allosteric modulator binds to a part of an ion channel to change the characteristics (e.g., the movement of ions across the chain).

Question 23

Describe the difference between an antagonist and an agonist.

Answer 23

An antagonist blocks or reduces the agonist mediated responses, whereas an agonist is a molecule that activates a receptor.

Question 24

What is wanted/required of a drug?

Answer 24

Have a desirable pharmacological action.
Achieve its therapeutic effect.
Have acceptable or no side effects.
Reach and remain in their target with the right concentration at/for the right time.
Be rapidly and completely removed from the body when no longer needed (as they affect homeostasis of the body).

Question 25

What are the three properties that affect drug-receptor binding?

Answer 25

Physico-chemical = electrostatic charges of drug and binding site.
Steric = physical shape/molecular structure of the drug and binding site.
Affinity = the strength of the agonist-receptor interaction (how well they bind).

Question 26

Define the term ‘pharmacogenomics’.

Answer 26

The way an individual’s genetics attributes the affect response to therapeutic drugs.