Lecture 36 - Drugs are Poisons Flashcards
Give an example of a nicotinic agonist and antagonist
Agonist: nicotine
Antagonist: d-turbocurarine
Give an example of a muscarinic agonist and antagonist
Agonist: muscarine
Antagonist: atropine
Give an example of a AChE inhibitor, and the source
Physostigmine
Calabar bean from the ordeal plant
What plant does nictine come from?
Nicotiana tobacum
What plant does muscarine come from?
Amanita muscara
What plant does atropine come from?
Atropa beladonna
Where does Digitalis come from?
Foxgloves
Who was the start of modern therapeutics?
What did he discover?
William Withering
The effects of foxglove extracts
Describe the mode of action of digitalis
- Inhibits Na+/K+ ATPase
- Na+ build up in cells
- Decreased Ca2+ extrusion
- Increased cardiac contractile force
What is the overall effect of Digitalis?
Increased cardiac force
What can digitalis be used for to bring about a favourable response?
Heart failure
What adverse effects can Digitalis bring about?
Cardiac arrythmias
What is ‘the right dose’
AKA The Therapeutic dose
More than lowest effective dose
Less than highest safe dose
Not definite: rather a continuum
What are the good and bad outcomes of Paracetamol?
Good:
- analgesic
- (inhibition of PG synthesis in the brain)
Bad:
- liver necrosis
What do we have to think about when taking paracetamol?
How much will relieve my headache?
At what point will i start to damage my liver?
What do we have to think about when taking digitalis?
How much will stimulate the cardiac muscle?
When will I start to get cardiac arrythmias?
Which process brings about the positive and negative effects of digitalis?
Blockage of Na/K ATPase
What is the right dose not ‘all-or-none’?
People are different
It is a continuum
What are on-target and off-target effects?
On-target: too much of a good thing
Off-target: lack of specificity
What is the relationship between Terfenadine and Fexofenadine?
Fexo. is a product of CYP metabolism of Terf.
What is the bioavailability of Terfenadine?
Nearly zero
How does grapefruit interact with terfenadine?
- Dihydrobergamottin inhibits CYP
- Terf not converted to Fex.
- Terf. now bioavailable
- Torsades de Pointes (tachycardia)
Which drugs have their bioavailability increased by grapefruit juice?
Simvastatin
Terfenadine
Which drugs will be affected by grapefruit juice?
Any drug that is metabolised by that particular CYP
Two drugs are metabolised by the same CYP. What happens if these drugs are taken at the same time?
Competition for metabolism
Increased half life
Why are selective drugs better?
They bring about the desired action at a much lesser concentration
What is the ABCD of drug interactions?
A: augmented
B: bizarre
C: chronic
D: delayed
Describe an example of type A ADR
Digitalis
Taking too much leads to cardiac arrythmias
Describe an example of type B ADR
Penicillin
- Some people have allergies to penicillin
- idiosyncratic
What is Type B ADR normally due to?
Phenotypic variation in metabolism
Give an example of Type C ADR
Cocaine:
- tolerance
- dependence
Bex, Vincent’s
- nephropathy
Adrenal insufficiency
- when taking glucocorticoids
What are some examples of Type D ADR?
Cancer
Infertility
Thalidomide use
- Phocomelia
- antagonist of angiogenesis in limbs
Explain the ADR of morphine
A: constipation, respiratory depression
B: allergy
C: addiction
D: withdrawal
Explain the ADR of cortisone
A: immunosuppresion
C: thin skin
D: adrenal insufficiency
Which type of ADR is predictable?
Type A
Who said that all drugs are poisons?
Paracelsus
