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Questions and Answers
What is meant by Emax in the context of spare receptors?
What is meant by Emax in the context of spare receptors?
What clinical benefit do spare receptors provide in cases of pathological receptor down-regulation?
What clinical benefit do spare receptors provide in cases of pathological receptor down-regulation?
Which statement accurately describes a partial agonist?
Which statement accurately describes a partial agonist?
What is the relationship between potency and the number of receptors?
What is the relationship between potency and the number of receptors?
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What characterizes reversible competitive antagonism?
What characterizes reversible competitive antagonism?
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What does IC50 represent in pharmacology?
What does IC50 represent in pharmacology?
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Which of the following is NOT a type of antagonist?
Which of the following is NOT a type of antagonist?
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What occurs when an agonist achieves Emax at subBmax?
What occurs when an agonist achieves Emax at subBmax?
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What does the term 'affinity' refer to in drug-receptor interactions?
What does the term 'affinity' refer to in drug-receptor interactions?
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Which of the following statements about agonists is true?
Which of the following statements about agonists is true?
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What is the primary purpose of antagonists in pharmacology?
What is the primary purpose of antagonists in pharmacology?
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How does drug concentration affect drug response?
How does drug concentration affect drug response?
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What is defined as the ability of a drug-bound receptor to produce a response?
What is defined as the ability of a drug-bound receptor to produce a response?
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Which of the following is NOT a characteristic of a drug's target receptor?
Which of the following is NOT a characteristic of a drug's target receptor?
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What governs the binding of a drug to its receptor?
What governs the binding of a drug to its receptor?
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In the context of drug action, what does potency refer to?
In the context of drug action, what does potency refer to?
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Flashcards
Medical Pharmacology
Medical Pharmacology
The study of how drugs interact with the body, including their mechanisms of action, effects, and how they are metabolized and eliminated.
Drug Target
Drug Target
A specific molecule or site on a molecule to which a drug binds to produce its effect. Often, these are proteins, but can also include DNA.
Pharmacodynamics
Pharmacodynamics
The study of how drugs affect the body at the cellular and molecular level, including their mechanisms of action and how they interact with receptors.
Receptor
Receptor
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Affinity
Affinity
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Efficacy
Efficacy
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Potency
Potency
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Agonist
Agonist
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Spare receptors
Spare receptors
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Emax achieved at subBmax
Emax achieved at subBmax
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SubEmax achieved at Bmax
SubEmax achieved at Bmax
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Clinical importance of spare receptors
Clinical importance of spare receptors
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Spare receptors in disease states
Spare receptors in disease states
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EC50
EC50
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Partial agonists
Partial agonists
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Full agonists
Full agonists
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Study Notes
Membranes and Receptors - Session 8.2
- The lecture aims to provide an understanding of drug-receptor interactions to aid in clinical practice.
- The quantitative relationship between drug concentration and response, agonist and antagonist drug action will be discussed.
- Key terms that will be defined include: affinity, efficacy, potency, agonist, antagonist, and partial agonist.
Drugs and Their Targets
- Medical pharmacology is the study of how chemicals (drugs) interact with the human body.
- Many drugs exert their effects by interacting with targets, predominantly proteins.
- Some antimicrobial and antitumor drugs bind to DNA.
Pharmaceutics, Pharmacodynamics, and Pharmacokinetics
- Pharmaceutics: drug formulation for a specific route of administration.
- Pharmacodynamics: interactions between a drug and its target (e.g., a receptor). Outcomes include efficacy, Emax, E, Bmax, B, potency, TD50, and TI.
- Pharmacokinetics drug + body tissue interactions (apart from D+T). Outcomes include ADME (absorption, distribution, metabolism, and elimination).
Drug-Target Interactions
- Many drug targets are receptors.
- A receptor is a protein with a site for binding endogenous ligands (e.g., steroid receptors).
- If a drug binds to a non-endogenous ligand site, this site is called an acceptor (e.g., enzyme blocker).
Receptor Types
- Receptors come in various types.
- Ion Channels: Direct mechanisms - opening/closing ion channels.
- Enzymes: inhibit reaction and produce active drugs.
- Transporters: block transport, alter compounds and produce abnormal, new products.
Relevance of Drug Concentration
- One mole contains 6 x 1023 particles.
- A 1 molar solution contains 1 mole in 1 liter.
- Molecular Weight (MW) × Molarity (M) = Grams per Liter
- Example: Acetylcholine (ACh) has a molecular weight (MWt) of 146.21 which translates to 146.2 g/L in a 1 molar solution.
Drug-Receptor Interactions (Detailed)
- Most drugs bind reversibly to receptors.
- Binding is governed by association and dissociation rates.
- Binding obeys the law of mass action, being related to the concentrations of reactants and products.
Affinity, Efficacy, and Potency
- Affinity: strength of drug binding to the receptor.
- Efficacy: ability of a drug-bound receptor producing a response.
- Agonist: possesses both affinity and efficacy.
- A + R ↔ AR → AR* → Response. (A = drug, R = receptor; AR* = activated receptor complex)
Agonists and Antagonists
- Agonists: bind to receptors and cause a response (affinity and efficacy).
- Antagonists: bind to receptors but do not cause a response (affinity only). They block the effects of agonists.
Drug Concentration and Drug Response
- Drug response is generally proportional to the number of receptor sites bound by the drug.
- Target receptors exist in different tissues throughout the body.
- Bmax: maximum number of receptors.
- B50: concentration where 50% of receptors are bound.
- Kd: dissociation constant.
- Emax: maximum response.
Partial Agonists
- Drugs often cannot produce a maximum effect, even at full receptor occupancy; these are partial agonists.
- A partial agonist's EC50 is equal to its Kd , the dissociation constant.
- The potency is dependent on both affinity and efficacy
Spare Receptors
- Spare receptors are unoccupied receptors when the agonist achieves its maximum effect (Emax).
- It is a concept reversed for partial agonists since submaximal effect is achieved at Bmax.
- Clinical implications include hormone and energy economy and maintained drug efficacy.
Antagonism
- There are three major types of antagonism:
- Reversible competitive.
- Irreversible competitive.
- Non-competitive.
- The IC50 is the concentration of an antagonist required to cause 50% inhibition.
Effects of Varying [Antagonist]
- Increasing the concentration of antagonist leads to greater inhibition of the agonist's effects.
Reversible Competitive Antagonism
- This is the most common type of antagonism in therapeutics.
- It relies on a dynamic equilibrium between ligands and receptors.
- High agonist concentrations can overcome the effect of the antagonist.
Other Types of Antagonism
- Irreversible competitive: Antagonist dissociates slowly or not at all. Higher antagonist concentrations can suppress overall maximal response.
- Non-competitive: Antagonist binds to a different site from the agonist, affecting its efficacy
Potency Comparisons
- The potency of two drugs can be compared using their EC50 values; smaller EC50=more potent drug.
- The maximum response values are also a relevant aspect to consider when evaluating drugs.
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Description
This quiz focuses on drug-receptor interactions crucial for clinical practice. It covers the quantitative relationship between drug concentration and response, along with key pharmacological terms such as affinity, efficacy, and potency. Test your knowledge on how drugs interact with their targets and the fundamentals of pharmaceutics, pharmacodynamics, and pharmacokinetics.
