Lecture 36 - Drugs are Poisons

Question 1

Give an example of a nicotinic agonist and antagonist

Answer 1

Agonist: nicotine

Antagonist: d-turbocurarine

Question 2

Give an example of a muscarinic agonist and antagonist

Answer 2

Agonist: muscarine

Antagonist: atropine

Question 3

Give an example of a AChE inhibitor, and the source

Answer 3

Physostigmine

Calabar bean from the ordeal plant

Question 4

What plant does nictine come from?

Answer 4

Nicotiana tobacum

Question 5

What plant does muscarine come from?

Answer 5

Amanita muscara

Question 6

What plant does atropine come from?

Answer 6

Atropa beladonna

Question 7

Where does Digitalis come from?

Answer 7

Foxgloves

Question 8

Who was the start of modern therapeutics?

What did he discover?

Answer 8

William Withering

The effects of foxglove extracts

Question 9

Describe the mode of action of digitalis

Answer 9

1. Inhibits Na+/K+ ATPase
2. Na+ build up in cells
3. Decreased Ca2+ extrusion
4. Increased cardiac contractile force

Question 10

What is the overall effect of Digitalis?

Answer 10

Increased cardiac force

Question 11

What can digitalis be used for to bring about a favourable response?

Answer 11

Heart failure

Question 12

What adverse effects can Digitalis bring about?

Answer 12

Cardiac arrythmias

Question 13

What is ‘the right dose’

Answer 13

AKA The Therapeutic dose

More than lowest effective dose
Less than highest safe dose

Not definite: rather a continuum

Question 14

What are the good and bad outcomes of Paracetamol?

Answer 14

Good:

• analgesic
• (inhibition of PG synthesis in the brain)

Bad:
- liver necrosis

Question 15

What do we have to think about when taking paracetamol?

Answer 15

How much will relieve my headache?

At what point will i start to damage my liver?

Question 16

What do we have to think about when taking digitalis?

Answer 16

How much will stimulate the cardiac muscle?

When will I start to get cardiac arrythmias?

Question 17

Which process brings about the positive and negative effects of digitalis?

Answer 17

Blockage of Na/K ATPase

Question 18

What is the right dose not ‘all-or-none’?

Answer 18

People are different

It is a continuum

Question 19

What are on-target and off-target effects?

Answer 19

On-target: too much of a good thing

Off-target: lack of specificity

Question 20

What is the relationship between Terfenadine and Fexofenadine?

Answer 20

Fexo. is a product of CYP metabolism of Terf.

Question 21

What is the bioavailability of Terfenadine?

Answer 21

Nearly zero

Question 22

How does grapefruit interact with terfenadine?

Answer 22

1. Dihydrobergamottin inhibits CYP
2. Terf not converted to Fex.
3. Terf. now bioavailable
4. Torsades de Pointes (tachycardia)

Question 23

Which drugs have their bioavailability increased by grapefruit juice?

Answer 23

Simvastatin

Terfenadine

Question 24

Which drugs will be affected by grapefruit juice?

Answer 24

Any drug that is metabolised by that particular CYP

Question 25

Two drugs are metabolised by the same CYP. What happens if these drugs are taken at the same time?

Answer 25

Competition for metabolism Increased half life

Question 26

Why are selective drugs better?

Answer 26

They bring about the desired action at a much lesser concentration

Question 27

What is the ABCD of drug interactions?

Answer 27

A: augmented B: bizarre C: chronic D: delayed

Question 28

Describe an example of type A ADR

Answer 28

Digitalis | Taking too much leads to cardiac arrythmias

Question 29

Describe an example of type B ADR

Answer 29

Penicillin - Some people have allergies to penicillin - idiosyncratic

Question 30

What is Type B ADR normally due to?

Answer 30

Phenotypic variation in metabolism

Question 31

Give an example of Type C ADR

Answer 31

Cocaine: - tolerance - dependence Bex, Vincent's - nephropathy Adrenal insufficiency - when taking glucocorticoids

Question 32

What are some examples of Type D ADR?

Answer 32

Cancer Infertility Thalidomide use - Phocomelia - antagonist of angiogenesis in limbs

Question 33

Explain the ADR of morphine

Answer 33

A: constipation, respiratory depression B: allergy C: addiction D: withdrawal

Question 34

Explain the ADR of cortisone

Answer 34

A: immunosuppresion C: thin skin D: adrenal insufficiency

Question 35

Which type of ADR is predictable?

Answer 35

Type A

Question 36

Who said that all drugs are poisons?

Answer 36

Paracelsus