SAQ's

Question 1

Which analogy can be used to describe how a drug binds to its receptor?
Using an example briefly describe how this process works in the body?

Answer 1

The receptor is like a lock, and the drug is the key. A drug must fit precisely into its receptor to activate or inhibit it.
Oxytocin is a hormone used to augment/induce labour. Oxytocin (key) acts on receptors (locks) within the uterus causing the muscles to contract and progress labour.

Question 2

What is first-pass metabolism?

Answer 2

Process where a drug is metabolized by the GI tract/liver before reaching the systemic circulation. Drugs given orally will go through this process. Drugs given by IV route will bypass this.

Question 3

Salbutamol is an agonist drug and propranolol is an antagonist drug. Explain these two terms in relation to the action of these drugs.

Answer 3

Agonist: Bind to a receptor and produce a response.
Antagonist: Bind to a receptor but do not produce a response and opposes action of agnonists.

Question 3

Explain what occurs during phase 1 and phase 2 of metabolism undertaken by Cytochrome P450 enzymes?

Answer 3

Phase 1: Oxidation/hydrolysis by Cytochrome P450 enzymes.
Phase 2: Conjugation of metabolites/drug to make the drug more water-soluble to enable elimination via the kidneys.

Conjugation = attaching of chemical group to drug/metabolite.

Question 4

What is the role of plasma proteins in drug distribution?

Answer 4

Plasma proteins control how much of the drug stays in the bloodstream and how much is free to distribute into tissues and take action. Only unbound/free drug can act on receptor sites. Drugs extensively bound to proteins will have a low Vd.

A low Vd because they are ‘stuck’ n the blood.

Question 5

What is meant by the “therapeutic range” of a drug? Give an example of a
common drug with a narrow therapeutic range.

Answer 5

The dosage range that achieves a therapeutic effect. Determines the drug concentration for ineffective, effective or toxic effect. E.g., Lithium.

Question 6

Briefly discuss the potential difficulties in drug administration with older
people?

Answer 6

Polypharmacy. Co-morbidities. Differences in pharmacokinetics.

Question 7

Describe 3 advantages and disadvantages pulmonary route of drug
administration.

Answer 7

+ve: Avoids first-pass metabolism, rapid absorption through lung tissue, systemic effects lessened.
-ve: Inhaler technique may affect drug availiability. Cough reflex.

Question 8

What is pharmacokinetics? How does it differ from pharmacodynamics?

Answer 8

It is what the body does to the drug including ADME. It differs because pharmacodynamics is what the drug does to the body.

Question 9

Explain the following terms -
a. Absorption
b. Distribution
c. Metabolism
d. Excretion

Answer 9

A = Process by which a drug goes through to enter systemic circulation.
D = Process by which drug penetrates tissue at receptor site.
M = Process by which drug is broken down within the body.
E = Process by which the drug is eliminated by the body.

Question 10

Explain the following terms –
a. Bioavailabilty
b. Onset
c. Peak
d. Duration

Answer 10

Bioavailability = Proportion of drug reaching systemic circulation.
Onset = Time taken for a drug to elicit a therapeutic response.
Peak = Time taken for drug to reach maximum therapeutic response.
Duration = Time a drug concentration is sufficient to elicit a therapeutic response.

Question 11

What is affinity?

Answer 11

How well the drug binds to a chemically sensitive receptor.

Question 12

Drugs are usually transported by binding to proteins, name 4 protein targets –

Answer 12

RICE:
Receptors: Bind to receptor to trigger or block signals.
Ion Channels: Regulate flow of ions in/out of cells.
Carrier Proteins: Bind to transport proteins to affect movement of molecules across cell membranes.
Enzymes: bind to enzymes to inhibit/enhance their action.

Question 13

Outline 3 reasons why proteins make good targets for drugs?

Answer 13

Specificity: Drugs can be designed to interact with specific proteins to produce a specific response.
Proteins are involved in physiological responses therefore they can be targeted to provide a therapeutic effect.
Each organ has a protein distinctive to that organ/tissue.

Question 14

Different types of drug targets exist in the body. Please describe the following
a. Agonist
b. Partial agonist
c. Antagonist
d. Partial antagonist

Answer 14

Agonist = Binds to receptor to increase its activity.
Partial agonist = Only elicit a smaller maximal response.
Antagonist = Binds to its target receptor but does not elicit a response. Blocks agonists.
Partial antagonist=

Question 15

Please explain the following pharmacology terms
a. Efficacy
b. Potency
c. Down-regulation
d. Up-regulation

Answer 15

Efficacy: defines how well a drug achieves a response.
Potency: Amount of drug required to produce maximal response.
Down-regulation: Continuous exposure to an agonist = receptors reduce in number and desensitise.
Up-regulation = Cell receptors increase due to lack of stimulation by agonist or exposure to antagonist.

Potency is dependent on both affinity of a drug to its receptor site and its efficacy (how well it achieves a response).

Question 16

Why can salbutamol cause tachycardia?

Answer 16

Salbutamol is a β2 agonist and targets receptors in the bronchioles in the
lungs to cause bronchodilation however it is not specific so can also bind to
β1 receptors in heart and produce the same effect as adrenaline. This causes
tachycardia.

Question 17

What is the key difference between as ion channel and a carrier protein?

Answer 17

A carrier protein requires energy in the form of ATP to transport ions across
membranes. An ion channel does not- passive.

Question 18

Explain how Serotonin selective receptor inhibitors (SSRIs) work?

Answer 18

They work by blocking the reuptake of serotonin in the brain, which increases the amount of serotonin available to pass messages between nerve cells.

Question 19

Describe the 4 different types of enzyme inhibition?

Answer 19

Competitive:
Non-Competitive:
Reversible:
Irreversible: Permanent loss of function until more enzyme is made.

Question 20

Why is pharmacology important?

Answer 20

To inform us of:
Dosage
Frequency
DDI’s
ADR’s
Changing dose/frequency for different conditions.