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meds2002 Flashcards

1
Q

What are some targets for drugs at the cell surface?

A

1) transporters
2) receptors
3) ion channels

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2
Q

What are some targets for drugs in the cytoplasm?

A

1) enzymes
2) nuclear receptors
3) protein synthesis

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3
Q

examples of drugs on receptors

A

agonists
antagonists
modulators

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4
Q

examples of drugs on ion channels

A

blockers

modulators

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5
Q

examples of drugs on enzymes

A

inhibitors

false substrates

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6
Q

examples of drugs on transporters

A

blockers

false substrates

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7
Q

where do we get compounds from?

A

natural prdoucts-herbs, animal products
combinatorial chemistry
random screening of compounds using high through put assays
structure based drug design

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8
Q

What are some things that makes a good drug?

A 
effective
non-toxic
minimal side effects
bioavailability
mechanisms of action
inexpensive to manufacture
acceptable route of administration
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9
Q

What are some factors affecting bioavailability

A 
different pH environments of the body
diffusion through cell membranes
blood brain barrier
metabolism
off target binding
effects can be modulated by administration route
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10
Q

why is pKa important to looked at

A

we need to predict what form a drug is in

Ionic forms of drugs penetrate membranes slowly

ionic bonds can lead to strong interactions with target

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11
Q

Nicotinic acetylcholine receptor

A

ligand gated ion channel
5 subunits come together to form an ion channel
multiple subtypes of alpha and beta subunits

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12
Q

mAChR

A

g protein
7 transmembrane domain
5 subtypes

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13
Q

example of ion dipole or dipole-dipole bonds

A

quaternary amine of acetylcholine found close to the lone pair of electrons on an oxygen atom of the hydroxyl group of a serine residue

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14
Q

sidechain of leucine as an example of hydrophobic interactions

A

The side chain of a leucine residue prefers to be in close proximity to an aromatic group of nicotine, and avoid polar groups such as the tertiary amine of nicotine

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15
Q

properties of protein backbone

A

some protein backbones can form hydrogen bonds

lots of Os and Ns

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16
Q

Why is oral blood not always recommended

A

Oral drugs usually means that the drug in the intestine is absorbed into the portal circulation. The portal blood is first delivered to the liver. The liver is the major organ of biotransformation

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17
Q

What are some things that help with drug absorption

A

Solute carrier transporters.
They help increase intestinal uptake of numerous drugs

They have a physiological role in anion and cation transporters

i think this includes both passive and active transport pathways

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18
Q

Drug absorption: role of ABC efflux transporters

A

the example given was P glycoprotein.

They basically are located in enterocytes, and they decrease drug uptake into the portal circulation

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19
Q

How does drug ionization affect drug disposition in tissues

A

ionization influences drug movement between aqueous and lipid environments

Strong acids/bases-ionised at any pH

weak acids/bases-extent of ionization depends on the pH of the aqueous environment

For a weakly acidic drug, an increase in H+ suppresses ionisation and favours diffusion through a membrane

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20
Q

What is the significance of the intestine in drug metabolism

A

Some drugs are extensively metabolised in enterocytes, whereas some are minimally metabolised

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21
Q

What is the second most important contributor to a decreased portal circulation

A

A newly absorbed drug enters the portal circulation
The plasma proteins may limit the free drug concentration

and only unbound drug in plasma can enter tissues

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22
Q

What kind of compounds do plasma protein bind to

A

See supplementary online file 2
serum albumin binds many acidic drugs

whereas a acidglycoprotein binds many basic drugs

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23
Q

If a drug is extensively metabolised and has a high first pass effect, hepatic extraction is:

A

high

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24
Q

bioavailability definition

A

It is an important pharmacokinetic quantity describing how much of a dose is available after administration

The bioavailability of an intravenous dose is 100%

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25
Why do we have intraocular and intranasal injections
Eye drops and nose drops are intended to act locally. This generally minimises systemic effects However, it can get disproportionately high plasma concentrations of drugs because some drug can enter the systemic circulation
26
How do biotransformation enzymes help with the elimination of different enzymes
they convert lipid soluble chemicals into more polar products These are more readily eliminated Usually metabolites are also less active However, some important drugs are prodrugs that themselves have low activity pro drugs are activated by metabolism
27
Where does biotransformation occur in the body?
``` Liver (1) Lung(0.1 to 0.2) intestine (0.06) placentra (0.05) adrenals (0.02) skin(0.01) ```
28
What is the major class of phase I biotransformation enzymes?
CYPs, cytochrome P450s
29
How are CYPs different from other drugs
CYPs act on diverse substrates (low substrate specificity
30
What are some CYP structure and function notes
All CYPs have a haem group involved in oxygen activation The polypeptide chain differs between CYPs and controls substrate specificity Each CYP is encoded by a different gene Variations in amino acid sequence often influence enzyme function
31
What are some important properties of CYPs that can influence therapy
They are readily inhibited-giving rise to pharmacokinetic drug-drug interactions Some are inducible-where exposure to drugs and chemicals can increase the amount of the CYP in liver Often subject to extensive pharmacogenetic variation
32
What is the major CYP in the human liver? | What does it do
CYP3A4 readily inhibited, highly inducible many drugs 60% metabolised by this enzyme
33
What is the implication of grapejuice inhibition on CYP3A4
grapefruit juice contains a chemical that inhibits intestinal metabolism and allows more of a dose to be absorbed into the systemic circulation
34
How might CYP genes be activated
PXR is a transcriptional regulator of CYP. It helps upregulate CYP RXR works with PXR to activate CYP genes CAR was also mentioned
35
CYP2D6
is debrisoquine hydroxylase can add or remove functional groups-specifically hydroxylation, demethylation and dealkylation It could also activate some prodrugs
36
What is the difference between having a single nucleotide polymorphism in coding regions and regulatory regions
If it is seen in coding regions, it could affect protein function if it is seen on regulatory regions, it can affect the amount of protein synthesised
37
The CYP2D6 gene is highly polymorphic
extensive metabolisers carry 2 active alleles poor metabolisers carry 2 nonfunctional alleles intermediate metabolisers carry 2 low activity alleles or 1 active and 1 inactive allele ultrarapid metabolisers carry multiple copies of CYP2D6
38
What are 2 forms of gene polymorphism?
SNP and VNTR
39
What is phase 2 metabolism
The phase 1 metabolites are conjugated with very polar endogenous molecules such as glucuronic acid and sulfate after phase ii conjugates, they are easily excreted in urine and faeces
40
Why are polar molecules more easily secreted
Because they are more hydrophilic, and therefore more water soluble. They prevent reabsorption
41
How do polar molecules move out of cells
ABC transporters They are open dimers, binding of ATP produces a conformational shift The substrate is effluxed and ATP is dephosphorylated to produce ADP The starting conformation is restored to accept further substrate present in the cell
42
Where are drug metabolites eliminated in the systemic and faeces?
Transporters can direct the drug metabolite back into the systemic circulation for elimination in urine or bile for elimination in faeces
43
Renal elimination(urine)
glomerular filtration active tubular secretion tubular reabsorption
44
What kind of drug is removed at glomerular filtration
removal of free drug-drug which is not bound to plasma proteins
45
What kind of drug is removed at active tubular secretion
Drug which had been transported from blood into urine
46
What kind of drug is favoured at tubular reabsorption
passive process in which drug in urine diffuses back into blood favours unionised drug urinary pH important
47
What is the point of urinary alkalinisers
They transiently increase pH which facilitates excretion of weak acids as they remain more ionised and remain in urine non-ionised acidic drug in blood can move across tubular membrane so ionised acidic drug decreases reabsorption
48
What is the physiological role of bile
excretion of cholesterol absorption of lipids stimulation of intestinal motility Drug conjugates formed in liver can be excreted in bile and then deposited in intestine
49
what are the 2 major mechanisms for drugs to appear in faeces
By not being absorbed into the systemic circulation so drug passes along the intestine by being absorbed, excreted in bile and then being deposited back into the intestine
50
What happens after biliary excretion of drugs
After biliary excretion, gut bacteria can cleave phase ii drug conjugates, for example glucuronide is removed This restore drug or phase 1 metabolite,
51
Enterohepatic recycling
It could happen sometimes apparently. This may produce a secondary phase
52
Pulmonary elimination
The major organ of excretion for gases and volatile substances that do not require metabolism The breathalyzer test quantifies the pulmonary excretion of ethanol
53
Elimination in breast milk
unknown
54
Affinity
refers to the drug's ability to bind to the target quantified as the concentration of drug required to occupy 50% of target proteins
55
intrinsic efficacy
the maximal effect a drug can produce on an tissue as a proportion of the maximal effect of a full agonist on that tissue full agonist->intrinsic efficacy=1 antagonist->intrinsic efficacy =0 partial agonist=intrinsic efficacy between 0 and 1
56
What factors may intrinsic efficacy account for
more than 1 activated state of a receptor | binding to a small propotion of the total receptors can give a maximum response
57
potency
the concentration of a drug that causes a specified effect a drug that causes a specified effect at a smaller concentration is more potent
58
Why do we get side-effects from drugs sometimes
Because no drug is totally specific to a target, so we get side effects
59
What is selectivity
ability of a given drug concentration to produce one effect over another
60
What are 3 stages of drug action in ligand receptor interactions
1) binding 2) conformational change and transduction 3) response
61
ligand
a molecule that binds to an active site on a macromolecule
62
agonist
a ligand that binds to and activates a receptor to produce a response in the cell
63
antagonist
a ligand that binds to a receptor but does not activate it. Agonists reduce the probability of an agonist binding to the receptor thus reduce or block its action
64
Allosteric modulators
A molecule that binds to an active site on a macromolecule to enhance or reduce a response from an agonist it has no effect on its own and may alter affinity or intrinsic efficacy of the agonist

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