Pharmacology

Question 1

Define pharmacology, drugs and medicines

Answer 1

Pharmacology is the study of the effects of drugs on living organisms

Drugs are chemicals that produce biological effects

Question 2

What are the different categories of drugs?

Answer 2

Medicines: Intention of therapeutic effect
Substances of abuse e.g. cocaine

Endogenous substances e.g. insulin or adrenaline (to treat anaphylaxis)

Research tools: No therapeutic benefit, but useful for understanding how cells work. Form part of the drug development process.

Question 3

What is the difference between adrenaline and bisoprolol

Answer 3

Adrenaline: stimulates β-adrenoceptors in the heart. ⇡ HR and contraction, prescribed to a patient to increase heart activity eg during cardiac arrest
Bisoprolol: Beta-blocker, synthetic drug that acts at β-adrenoceptors to prevent/reduce action of adrenaline. Reduces HR and contraction. Treats CV conditions like angina and heart failure.

Question 4

Describe the properties of adrenaline with regards to tissue selectivity.

Answer 4

Adrenaline has tissue selectivity:
Heart: Increases heart rate and contraction strength
Blood vessels: Dilates skeletal arteries
Lungs: Dilates airways
Liver : Increases glycogen breakdown, increasing plasma glucose

Question 5

Describe properties of adrenaline with regards to chemical selectivity and potency.

Answer 5

Chemical Selectivity
The enantiomer (+)-adrenaline has ~100x greater biological effect than (-)-adrenaline
Drugs are very potent: Adrenaline acts at v low concs to produce significant increases in heart rate

Question 6

Explain general properties of receptors

Answer 6

Receptors are expressed in diff tissues. This is y adrenaline affects diff tissues- β-adrenoceptors are in heart, lungs, blood vessels, liver
Have highly selective targets: only specific drug structures bind to receptors
Amplify signals: small number of drug/receptor interactions initiate significant biological effects, thus why v low adrenaline concs ⇡ HR

Question 7

What does a b-adrenoreceptor look like?

Answer 7

B-Adrenoceptor is a large complex protein molecule.
Has transmembrane (in between lipid bilayer) regions with hydrophilic/lipophilic aa.s
Present in plasma membrane
Contains drug binding sites

Question 8

What else can be receptors?

Answer 8

Enzymes. Carrier molecules. Ion channels like Na+ can act as receptors

Many receptors are associated w the cell membrane so are accessible from the outside of the cell. Some drugs act inside the cell, e.g. steroids

Question 9

Differentiate between receptor, agonist and antagonist

Answer 9

RECEPTOR: A specific target molecule a drug interacts w to produce a cellular response e.g. Adrenaline and Bisoprolol both act at β-adrenoceptors.
AGONIST: A drug which binds to a receptor to produce a biological cellular response e.g. Adrenaline is an agonist that increases heart rate
ANTAGONIST: A drug which binds to a receptor but does NOT produce a biological effect. They bind to receptors and prevent agonists producing effects. eg Bisoprolol is an antagonist that blocks adrenaline-mediated increases in heart rate

Question 10

How can you classify drugs?

Answer 10

Drugs are classified segun a:
Clinical use: eg Bisoprolol is an anti-anginal drug
Target receptor: eg Bisoprolol binds to β-adrenoceptor. It’s a b-adrenoceptor antagonist (Beta-blocker), and Adrenaline is a b-adrenoceptor agonist

Question 11

Describe drug receptor interactions for AGONISTS

Answer 11

Step 1: the agonist binds to a receptor to produce a receptor-agonist-interaction. This is occupation.

The strength of this occupation is governed by affinity. V strong affinity= don’t need much agonist to bind to a receptor. The affinity constant, Ka tells us this info.

Affinity causes a change in the receptor. The receptor signals that it’s been activated. This produces efficacy (biological response).

Question 12

Describe drug receptor interactions for antagonists.

Answer 12

Step 1: the antagonist binds to a receptor to produce a receptor-antagonist-interaction. This is occupation.

The strength of this occupation is governed by affinity. V strong affinity= don’t need much antagonist to bind to a receptor. The affinity constant, Kant tells us this info.

Antagonists have affinity and an eqm Kant constant, but it has no efficacy, so no biological response

Question 13

What is the law of mass action?

Answer 13

Affinity is reversible. Law of mass of action: rr is determined by the concs of the reactants involved.

High AR conc means eqm shifts left and you have mas dissociation.

High A and Rfree conc means eqm shifts right, hay mas associtation to form receptor complexes.

BUT if conc of A keeps increasing, rr will slow down/reach a max bc solo hay a limited number of free receptors.

Question 14

Describe the affinity constant

Answer 14

The eqm constant (Ka or Kant) is when 50% of receptors are free and 50% are bound by drug

e.g. Ka of 50 nM means that at this conc, half the drug will be bound to its receptor. Each drug has it own Ka value.

Smaller Ka means agonist has a greater AFFINITY for receptor (it binds more).

The dotted line on the graph shows the K value bc 50% of the receptors are bound

Question 15

Draw equations to demonstrate agonists and antagonists binding to receptors

Answer 15

Question 16

What does it mean if a drug is really potent? What is EC50?

Answer 16

If a drug is really potent, it binds well to its receptor y for eso tiene great efficacy

EC50: the conc of drug at which 50% of max biological response is produced

Question 17

Explain the concept of amplification and why it is important

Answer 17

You don’t need full occupancy to give a max response bc receptors produce amplification. Only a small n0 of drug receptor interactions are needed for a larger bio response.

This is why drugs work at such low concs- eg In the graph solo tiene 25% occupancy to give max HR. If drugs only worked at high concs, they’re liable to bind to other things with adverse side-effects. Low concs enable selectivity.

Question 18

How will you know if the agonist or antagonist will bind to a receptor?

Answer 18

Agonist and Antagonist compete for the same binding site on a receptor. Both Agonist and Antagonist bind reversibly

If KAnt < KA, then the antagonist has greater affinity for receptors than the agonist. Agonist conc must increase to overcome antagonist binding to Receptors

Question 19

What is competitive antagonism?

Answer 19

Adrenaline in the presence of Bisoprolol causes a parallel shift in the curve to the right; ya necesitas much higher adrenaline concs to produce the same increase in heart rate.

This is competitive antagonism, or surmountable antagonism bc it can be overcome.

Question 20

Explain noncompetitive and irreversible antagonism.

Answer 20

Non-competitive antagonism: Antagonist binds on a diff site to the agonist on the same receptor. This prevents the agonist producing max bio response.

Irreversible antagonism: Antagonist binds irreversibly to the receptor through cv bonds.

Non-competitive and irreversible antagonists reduce number of receptors. They reduce max response even when agonist concentration is increased to high levels (Non-surmountable)

Question 21

Describe and explain ligand gated receptors

Answer 21

Ach binds to nicotinic receptors, ligand gated receptors that work v fast. On the outside hay an N and C terminal. This N-terminal is where the ligand will bind.

Ligand binds to the receptor. The 5 subunits change conformation, creating an ion channel opening in the centre. This channel allows ions to flow through so they move down their conc gradient. Ions flowing thru will change the charge inside the cell and lead to change in cell excitability. This is v fast, in ms.

Question 22

Describe G-protein-coupled receptors

Answer 22

e.g. β-adrenoceptors in heart

1 Single protein, span the transmembrane region 7 times. Outside N-terminal is the ligand-binding site. Inside C-terminal is where the G-proteins bind

Ligand binds to receptor. Hay activation of G-proteins bound to the C terminal. This produces intracellular messengers, leading to change in cellular function

Response time: seconds to mins e.g. ⇡HR during exercise

Question 23

Describe G proteins, how they react w and sin the presence of a ligand

Answer 23

GTP/GDP binding proteins consist of α, β, γ subunits. The G protein stimulates the receptor along w the drug to form a response.

When no ligand is bound: β and γ anchor the G proteins into the membrane. GDP is bound to the α subunit.

When a drug binds, receptor conformation changes, leaving an opening which allows GTP to enter. The α subunit now binds to GTP instead of GDP. This dissociates the α subunit from the β and γ subunit, and induces a cellular response.

This G α subunit has GTPase activity which breaks down GTP into GDP. This reestablishes resting state.

Question 24

What are the types of Alpha G receptor proteins and what functions do they have?

Answer 24

GαS stimulates formation of AC. The AC enzyme converts ATP into cAMP. GαI inhibits the pathway to reduce cAMP production.

Gαq stimulates PLC, which causes hydrolysis of PIP2 into DAG and IP3. IP3 goes into the cytosol, DAG activates PKC

Question 25

How do B-adrenoreceptors help increase heart rate?

Answer 25

B-adrenoreceptors are G protein coupled receptors linked to GαS, so when adrenaline binds to its receptor it stimulates cAMP production.

This stimulates Protein Kinase A (PKA), which ⇡ HR

Question 26

How do M2 receptors reduce HR?

Answer 26

M2 receptors in the heart are linked to GαI.

When Ach binds to M2 it inhibits AC and cAMP production which inhibits PKA. This decreases HR

Question 27

Outline the Gq-mediated phospholipase C pathway

Answer 27

Gq-mediated phospholipase C pathway: for actions such as muscle contraction

α adrenoreceptors are found in blood vessels. When NA binds to α adrenoreceptors it stimulates the Gq pathway

This stimulates PLC which breaks down PIP2 into DAG and IP3. PKC is activated. IP3 activates its own ligand gated receptor inside the cell. This forms a Ca2+ permeable pore, Ca2+ leaves the pore & enters the cell.

Question 28

Describe Tyrosine kinase receptors and their signal transduction mechanism

Answer 28

Monomer, 1 single protein subunit. 1 transmembrane domain. N-teminal binds ligand. C-terminal intracellular binds effector

Signal transduction mechanism: Ligand binding to monomers induces dimerisation- when 2 ligands each bind to a receptor and they join juntos

Dimerisation allows phosphorylation of the intracellular regions bc the C terminal has a tyrosine kinase in it. This causes a phosphorylated region that can bind to other cellular processes, causing change in cellular function

eg insulin ⇡ number of GLUT transporters on cell surface, leading to ⇡ glucose uptake from blood plasma into cells

This is slow response: minutes, hours, days

Question 29

Describe intracellular or nuclear receptors and their single transduction mechanism

Answer 29

Receptor found within cytoplasm of cell. Activated by endogenous drugs (steroids/hormones). These are lipophyllic so can cross the plasma membrane

Monomer, 1 single protein subunit. Has a DNA binding site. Its N-terminal binds heat shock protein (HSP) and agonist. Its C-terminal controls transcription.

Signal transduction mechanism: Drug crosses plasma membrane. Hormone displaces HSP and binds to N-terminal. Hormone/receptor complex enters nucleus and binds to hormone-responsive-element on a gene. This alters gene transcription

This is an even slower response: hours, days, months

Question 30

Who are the regulatory authorities in pharmacology?

Answer 30

UK – Medicines and Healthcare Products Regulatory Agency (MHRA)​

EU – European Medicines Agency (EMEA)​

USA – Food and Drugs Administration (FDA)​

Similar bodies exist elsewhere

Question 31

What is the yellow card scheme?

Answer 31

Yellow card scheme: A function of the MHRA which collates info about a medicine’s side affects.

The scheme inc medical devices, counterfeit products and e-cigarettes. Reports are now made by anyone, not just HCWs.​

It is a very powerful tool in monitoring drug safety

Question 32

Marketing authorisation depends on which 3 principles?

Answer 32

Safety – determines the relative risk for use, handling and manufacture ​

Quality – the drug is manufactured in a strictly controlled way and can be stored stably​

Efficacy – the drug produces a beneficial effect​

The case for these is submitted as comprehensive data involving studies done in vitro, in animals, healthy volunteers and in patients​

Question 33

What is the 1st phase of drug development?

Answer 33

Discovery research phase: basic research (industry/uni) identifies targets of interest.​

Next, we find useful molecules that could be optimised further, by screening chemical libraries. This needs time and automation.

W luck we might find ‘hits’. Hits interact w the target, but lack properties to make them a medicine. We then optimise hits into lead compounds until hay a candidate drug which may enter development.

Question 34

What limitations occur in the discovery research phase?

Answer 34

High failure rate​:

Target proves to be unimportant​

Sometimes the therapeutic target is strongly linked to a disease, but it isn’t the only factor and back-up mechanisms come into play. This=biological redundancy​

Target not ‘druggable’ (potency, selectivity, pharmacokinetic

Question 35

Describe what happens in pre-clinical development.

Answer 35

Chemical scale-up and final Good Manufacturing Practice- How is the drug made safely/economically on a large scale?​

ADME​: How is the drug absorbed, distributed, metabolised and excreted (animal studies)?​

Safety pharmacology​: any effects on major physiological systems (animal studies)​

Acute toxicology​: 2 animal species: Duration determines maximum length of initial clinical trials​

Pharmaceutics​: Determines best dosage formulation

Question 36

What are in vivo studies?

Answer 36

In vivo studies=a legal requirement in safety assessment.

Their design dictates the length of clinical trials that can be done in humans.

They’re done in species which best reflect the likely behaviour of the drug in a clinical setting.

Question 37

Describe clinical development

Answer 37

Question 38

Describe Safety and Toxicity Studies in Drug Development

Answer 38