Wk1- Pharmacodynamics (Mechanism of Action, Effects) Flashcards
What are the 4 targets of drug actions?
- Receptors
- Ion Channels
3- Enzymes
4- Carrier Molecules
One of the (4) targets of drug actions is RECEPTORS. What are receptors?
Receptors are protein molecules located in cell membranes/within cells.
One of the (4) targets of drug actions is RECEPTORS. What are some examples of receptors which drugs often target?
Receptors- opioid receptors, beta 1 receptors
Drugs can be classified as receptor agonists or receptor antagonists. What does this mean?
Receptor agonist= Ligand activates receptor
Receptor antagonist= Ligand blocks receptor
Drugs that target receptors can be ‘selective’ or ‘non-selective’. What does this mean?
Selective= drug targets 1 receptor
Non-selective= drug targets multiple receptors
One of the (4) targets of drug actions is ION CHANNELS. What are ion channels?
Ion channels= gateways in cell membranes which regulate the passage of ions
One of the (4) targets of drug actions is ION CHANNELS. What are some examples of ion channels which drugs often target?
Ion Channel Examples:
- Calcium channel
- Sodium channel
- Potassium channel
- Chloride channel
Drugs that target Ion Channels can be described as ‘ion channel blockers’ or ‘ion channel openers’. What does this mean?
Ion channel blockers= drug prevents opening of channel
Ion channel opener= drug facilitates ion movement through channel
One of the (4) targets of drug actions is ENZYMES. What are enzymes?
Enzymes are biological catalysts which control the rate of biochemical reactions in cells
Drugs that target enzymes can be described as ‘enzyme inhibitors’. What does this mean?
Enzyme Inhibitors= the drug inhibits the action of enzymes
Drugs that target enzymes can be described as ‘false substrates’. What does this mean?
False substrate= drug stimulates the production of abnormal metabolite
Drugs that target enzymes can be described as ‘pro drugs’. What does this mean?
Pro-drugs= drugs that are inactive and are converted within the body to an active drug
One of the (4) targets of drug actions is CARRIER MOLECULES (transporters). What are these?
Carrier Molecules/Transporters= these are molecules which transport drugs across lipid membranes
Drugs that target carrier molecules can be describes in 2 ways. What are these?
Drugs that target carrier molecules-
1) Transporter [facilitates transport]
2) Transporter Inhibitor [blocks transport]
Compare the terms ‘specificity’ and ‘selectivity’.
Specificity= the drugs effects & number of mechanisms involved. Drugs rarely have high specificity where they produce just 1 physiological response
Selectivity= the drugs target & its ability to be selective about its molecular target
What are ‘Agonists’?
Agonists= chemicals which bind to & activate the receptor in order to produce a biological response.
What are ‘Antagonists’?
Antagonists= A drug which occupies a receptor to inhibit other ligands binding. They therefore block activation of the receptor.
True or False- Agonists can either be endogenous or exogenous
True- agonists can be endogenous (created within the body) or exogenous (created outside the body- eg. drugs)
True or False- Antagonists can either be endogenous or exogenous
False- antagonists can only be exogenous (produced outside the body- eg. drugs). They can not be endogenous (created within the body)
What is the difference between a ‘full agonist’ and a ‘partial agonist’?
Full Agonist= Drugs that can stimulate the maximal physiological response if sufficient drug concentration is present
Partial Agonist= Even with the same occupancy of receptors as full agonists, partial agonists can only produce sub-maximal response. This is due to having partial efficacy/ability to elicit a response at the receptor site
Why can ‘Partial Agonists’ only produce a sub-maximal response even when bound to the same amount of receptor sites as full agonists (ie. same occupancy)?
Even with the same occupancy of receptors as full agonists, partial agonists can only produce sub-maximal response. This is due to having partial efficacy/ability to elicit a response at the receptor site
There are 6 classifications of Antagonism- This includes: Physiological Antagonism, Pharmacokinetic Antagonism, Chemical Antagonism…. and 3 MORE… What are the 3 others? [Hint- the 3 others are the more spoken about/known ones]
6 Classifications of Antagonism-
1- Physiological Antagonism
2- Pharmacokinetic Antagonism
3- Chemical Antagonism
4- REVERSIBLE COMPETITIVE ANTAGONISM
5- IRREVERSIBLE COMPETITIVE ANTAGONISM
6- NON-COMPETITIVE ANTAGONISM
What is the difference between ‘Reversible Competitive Antagonism’ and ‘Irreversible Competitive Antagonism’?
Reversible Competitive Antagonism= Drug binds to receptor site & blocks response, but CAN be reversed/overcome/displaced by adding more of the agonist ligand
Irreversible Competitive Antagonism= Drug binds to receptor site & blocks response, but CANNOT be reversed/overcome/displaced by adding more of the agonist ligand
What is the difference between ‘Non-competitive Antagonism’ and ‘Competitive Antagonism’?
a) Non-competitive Antagonism= Drug binds to an alternative site on the receptor (an ‘allosteric site’) in order to change the shape of the receptor, & therefore block a response.
b) Competitive Antagonism= Drug binds to the receptor site & blocks a response
What is an example of a-
1) Opioid Agonist
2) Opioid Antagonist
1) Opioid Agonist [binds & activates]= MORPHINE- binds to opioid receptors and activates a biological opioid effect
2) Opioid Antagonist [binds & blocks]= NALOXONE- binds to opioid receptors to prevent receptor activation and block the biological opioid effect
What are the 2 key Pharmacodynamic concepts that a ‘Concentration Response Curve’ graph can show us?
Concentration Response Curve Graph-
1) Drug Potency [dose needed to produce desired/required response]
2) Drug Efficacy [ability of a drug to elicit a response once bound]
What does ‘Potency’ mean?
Potency= The amount/dose of a drug required to produce the desired response
What does ‘Efficacy’ mean?
Efficacy= The ability of a drug to elicit a response once bound
What does ‘Affinity’ mean?
Affinity= The ability/tendency of a drug to bind to its target
[eg. A high affinity means the drug is more likely to bind to the receptor and spend a greater amount of time bound]
What would it mean if a drug had a-
1) High Affinity?
2) Low Affinity
High Affinity= means the drug is more likely to bind to the receptor and spend a greater amount of time bound
Low Affinity= the drugs is less likely to bind to the receptor and will spend a lower period of time bound
What would it mean if a drug had a-
1) High Efficacy?
2) Low Efficacy?
1) High Efficacy= the drug reaches a high maximum response (eg. max response of- 100% Response)
2) Low Efficacy= the drug reaches a low maximum response (eg. max response of- 60% Response)
What would it mean if a drug had a-
1) High Potency?
2) Low Potency?
1) High Potency= a drug is able to produce the desired response at a lower dose
2) Low Potency= a drug requires a high dose in order to produce the desired response
If 2 drugs (A & B) are administered at the same dose of 1000mg, but drug A has a higher POTENCY than drug B, what would this mean for the response/effect of each drug?
Drug A has a higher POTENCY than drug B. This means:
Drug A- will produce a more intense effect than drug B
Drug B- will produce a less intense effect than drug A, and will require a higher dose to reach the same effect as drug A
If 2 drugs (A & B) are administered at the same max dose of 10,000mg, but drug A has a higher EFFICACY than drug B, what would this mean for the response/effect of each drug?
Drug A has a higher EFFICACY than drug B. This means:
Drug A- will produce a more intense effect, with a higher maximum response %
Drug B- will produce a less intense effect than drug A, with a lower maximum response %
Concentration Response Curve graphs can show 3 components/ranges of a drug effect, including:
1) Sub-therapeutic range
2) Therapeutic range
3) Toxic range
What do these 3 ranges mean?
1) Sub-therapeutic range= dose does not produce a measurable biological effect
2) Therapeutic range= dose produces a measurable/desired biological effect
3) Toxic range= dose achieves little therapeutic effect, but significantly increases the risk of adverse reactions
What is plotted on the X and Y axis of a ‘Concentration Response Curve Graph’?
Concentration Response Curve Graph-
X axis= Dose/ Concentration administered
Y axis= Response
Look at this graph and compare the-
Efficacy & Potency of Drug A compared to Drug C
Efficacy- Drug A shows the same Efficacy as Drug C
Potency- but, Drug A is more Potent
Look at Drug B on this graph and compare the-
Efficacy & Potency of Drug B compared to Drug A and C
EFFICACY- Drug B shows lower Efficacy than Drug A and Drug C
POTENCY- Drug B is more Potent than Drug C, but less Potent than Drug A
How is a drugs Potency & Affinity linked? [Hint- does a higher affinity increase or decrease potency?]
The higher the AFFINITY, the greater the attraction between the drug and its receptor. This increases POTENCY as the drug is the more likely to interact with the receptor to produce a physiological response, even at a low concentration
Do Agonists & Antagonists both exhibit EFFICACY and AFFINITY? Explain why/why not
AGONISTS= exhibit both Affinity & Efficacy (ie. they are attracted to and bind to receptors [Affinity], and then have ability to activate elicit a response [Efficacy])
ANTAGONISTS= exhibit Affinity, but no Efficacy (ie. attracted to and occupies the receptor [Affinity], but they prevent receptor activation by blocking a response [NO Efficacy])
