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PA20308 > Medicines Design > Flashcards

Medicines Design Flashcards

1
Q

What can Microcrystaline Cellulose be used as in a tablet?

A

Diluent, disintegrant and lubricant

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2
Q

What is the point of a GC-MS?

A

The GC will create the M+

The MS then fragments this M+, which allows more in depth analysis to occur

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3
Q

Describe HPLC and Reverse Phase HPLC

A

HPLC - Silica gel is used, which is polar……and so polar molecules will stick to this greatly –> and not be eluted quickly

Reverse HPLC - Silica gel is capped with C18/8 chains, making it more non-polar.

When using this, polar molecules will be eluted first, as it has very low affinity for the silica….and higher affinity for the organic solvent (eg, methanol)

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4
Q

What is the most common reason for Gilberts Syndrome in caucasians?

A

A mutation in the promoter region of the gene

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5
Q

CYP enzmyes are usually…..

A

Stereospecific and regiospecific

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6
Q

What entantiomer is Esomeprazole (nexium)?

A

S enantiomer

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7
Q

What are the main things that can effect distribution in the body?

A

Protein binding - Especially for highly bound drugs with narrow therapeutic windows

The alteration of uptake and efflux pumps will also have an effect

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8
Q

What is Gilberts Syndrome?

A

Blocks enzymes that allow for glucaronic-acid conjugates to form

Also causes a build up of bilirubin in the body, which can cause jaundice

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9
Q

Explain Drug-Drug Interactions (DDIs)

A

These occur when two drugs are used together which are metabolised by the same enzyme

Perpetrator - The drug that is metabolised, and tha competes for the active site

Victim - The drug that is NOT metabolised, as a result of perpetrator –> this can cause toxic levels to be built up

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10
Q

What natural product can be used as a tablet binder that is organic-solvent soluble?

A

Ethyl Cellulose

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11
Q

When/how are mercapturates formed?

A

Once glutathione has reacted with the drug metabolite, so the mercapturate is formed to remove the conjugate

Hepatic (Y) - glu-tripeptidase is used to remove the Y-glu from the conjugate

Renal Cys-Gly dipeptidase is used to remove the glycine

Renal N-acetyl transferase (NAT) and Acetyl S CoA are used to form the mercapturate

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12
Q

When using Reverse Phase HPLC, how can you increase the rate at which a lipophillic drug is eluted?

A

By increasing the concentration of the organic solvent (mobile phase)

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13
Q

Where are most CYP450 enzymes found?

A

The endoplasmic reticulum of the liver

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14
Q

Explain what low hepatic ratio drugs are?

A

These dissociate slowly from plasma proteins

So they are sensitive to plasma binding

They have a high oral bioavaliability

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15
Q

In gas chromatography, what is seperation dependent on?

A

Vapour pressure

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16
Q

Describe the difference between Homology and Identity

A

Homology - The existence of a shared ancestry between several molecules

Eg, All AA are the same for every molecule, except certain AA such as leucine can be changed for other AAs

Identity - When in an AA sequance there is always one AA that is the same

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17
Q

How do PPIs work?

A

They pass through the body and into the bile canniculi

Here they become ionized, preventing them from moving out via the membrane

Once ionized, the PPI becomes functional…. irreversibly binding to the proton pump –> preventing H+ from being secreted into the stomach

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18
Q

What is the main purpose of phase 1 metabolism?

A

To reveal/create specific functional groups for phase 2 metabolism

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19
Q

What is the one class of solvent that is heavier than water?

A

Halocarbons

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20
Q

Explain what high hepatic ratio drugs are?

A

These are drugs that can easily dissociate from plasma proteins, and so can be metabolised in the liver easily and quickly

So they have a low bioavaliability –> due to a large first-pass effect

So Extraction ratio is practically equal to the hepatic blood flow

They are perfusion-rate limiting, and so are sensitive to blood-flow changes

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21
Q

Define Hepatic Clearance

A

The loss of the drug across the liver by metabolism and excretion

22
Q

What natural product could be used for enteric coating of tablets?

And why?

A

Cellulose Acetate Phthalate

As it is resistant to acid

It is insoluble in water and ethanol

23
Q

What are dermatophytes?

A

Fungi that can colonise the skin/nails/hair

Such as ringworm and athletes foot

24
Q

Draw the PPI pharmacophore

A
25
Q

When will bacteria produce spores?

A

When their nutrients have become exhausted

26
Q

Do protozas have cell walls?

A

No they do not have cell walls

27
Q

What is the main use of starch in tablets?

A

A disintegrant

28
Q

What are the 5 factors that affect the choice of preservative?

A

Intended application

Number/Type of Micro-organisms present

Safety, Stability and Cost

Micro-Environment –> eg, avaliability of the preservative and the presence of moisture

Physiochemical Properties of the Product –> eg, the pH of the product and the dilution factor

29
Q

Sporulation occurs for which type of bacteira?

A

Gram-Positive

30
Q

What were the structual modifications that came about to form ranitidine from cimetidine?

And what did this cause which is of benefit?

A

The cyanoguanidine unit is changed to a nitroketeneaminal group

A different heterocyclic ring was used

This caused fewer side effects, a longer mechanism of action (10x more active), no inhibition of CYP enzymes

31
Q

What do CYP oxidation reactions require to go ahead?

Eg, cofactors

A

NADPH, O2 and NADPH-cytochrome P450 Reductase

32
Q

How do moulds reproduce?

A

Always by spores!!

33
Q

What is SAR?

A

Structure Activity Relationship

This is where many compounds are synthesised that are similar to the lead compound

This allows us to see which functional groups and bond angles are vital for function

34
Q

What is more sensative for analysis…. UV or fluorescence?

A

UV = 1ug

Fluorescence = 1ng –> so more sensative

35
Q

What are the benefits of using Organic acids and Parabens as preservatives?

A

Active at low concentrations

Non Toxic

Cheap

Bacteriacidal and fungacidal (not sporacidal)

Long acting

36
Q

State some of the Intrinsic factors that affect drug metabolism

A

Age

Gender

Genetics –> variability in CYP enzymes

Polymorphisms

37
Q

What type of reaction occurs between glutathione and paracetamol?

A

1,4 conjugate addition

38
Q

Explain the effect of enzyme induction

A

As drugs are used for a prolonged period of time, enzymes become induced…allowing more of the drug to be metabolised

This decreases the drugs half-life

Therefore more drug is needed to reach the same therapeutic response

Tolerance will be reduced when the drug is not taken for a period of time

39
Q

What is intrinsic clearance?

And what effects it?

A

The ability of the liver to eliminate the drug in the absence of restrictions imposed by protein binding and blood flow to the liver

Inducers - Increases intrinsic clearance

Inhibitors - Decrease it

40
Q

Which types of preperations must be sterile?

A

Injectables and Opthalmic

41
Q

How do CYP450 enzymes work…??

A

Negative Catalysis

42
Q

What are the microbes that cannot be present in oral/topical preperations?

A

Oral - E.coli

Topical - S.aureus and P.aeruginosa

43
Q

What is the difference between pharmacodynamic and pharmacokinetic interactions?

A

Pharmacodynamic - When drugs/chemicals act of the same pharmacological target, or have the same therapeutic response or side effects

Pharmacokinetic - Things that causes a change in ADME

  • Eg, perpetrator and victim
44
Q

What is an internal standard?

A

A molecule that is very similar to the sample (eg, only adding an methyl) that elutes at the same place

It also must contain the same chromophore

We can then use this as a way of quantatativly analyse how much of the sample is present –> via the AUC

45
Q

What should preservatives do and not do?

A

Do - Rapid Kill

Broad spectrum of activity

Be cost effective

Be soluble in water/solvent of choice

Not do - Affect the characteristics of the formulation (eg, colour, taste or viscocity)

46
Q

Viruses are obligate intracellular.… what does this mean?

A

They cannot grow or replicate outside of their host

47
Q

What causes a molecule to be volatile?

A

Having no/few hydrogen bonding functional groups

This is because the evaporate, H bonds must be broken between the solute and water/solvent…..so the less possible bonds, the more likely that it is to evaporate

48
Q

What is QSAR?

A

Quantitative Structure Activity Relationship

This is done to identifity and quantify the physiochemical properties of the potential molecule without actually synthesising it

We can then use this data to see if certain changes will effect biological activity

49
Q

What is restrictive clearance?

A

When hepatic extraction is limited by protein binding

As its extraction efficiency is less/equal to the unbound fraction of the drug in the body

50
Q

What are external factors of drug metabolism?

And give a few examples?

A

These are factors that the person has been exposed to that isnt normal

Eg, Smoking, Drugs (DDIs), Liver disease

PA20308 (5 decks)

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