Pharmacodynamics
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Questions and Answers

What is the most common mode of drug action concerning enzymes?

  • Enzyme degradation
  • Enzyme inhibition (correct)
  • Enzyme stimulation
  • Enzyme activation

    • Which drug acts by inhibiting the COX enzyme?

  • Lisinopril
  • Amlodipine
  • Aspirin (correct)
  • Clorgyline

    • Which of the following drugs specifically blocks sodium channels to prevent nerve impulses?

  • Lidocaine (correct)
  • Furosemide
  • Clorgyline
  • Amlodipine

    • Which drug is a calcium channel blocker that is used for its antihypertensive effects?

    <p>Felodipine</p> Signup and view all the answers

    What is the mechanism of action for Monoamine reuptake inhibitors (MRIs)?

    <p>Inhibiting transport proteins</p> Signup and view all the answers

    What effect does Acetazolamide have on the body?

    <p>Blocks carbonic anhydrase activity</p> Signup and view all the answers

    Which of the following describes the action of diuretics like Furosemide?

    <p>Blocks Na/K/2Cl channels</p> Signup and view all the answers

    Which agent is specifically known to inhibit the MAO enzyme?

    <p>Clorgyline</p> Signup and view all the answers

    What is the primary effect of drugs like adrenaline and dobutamine on the heart?

    <p>They stimulate the heart to contract harder or beat faster.</p> Signup and view all the answers

    Which drug is an example of a non-receptor mediated mechanism of action that alters osmotic pressure?

    <p>Mannitol</p> Signup and view all the answers

    Which drug primarily acts by interfering with the functioning of foreign cells?

    <p>Antibiotics</p> Signup and view all the answers

    What is a characteristic of drugs that mediate changes in cellular function?

    <p>They result in alterations of intrinsic physiological processes.</p> Signup and view all the answers

    Which of the following examples illustrates a drug that has a chemical change effect on cellular environment?

    <p>Antacids neutralizing gastric acidity.</p> Signup and view all the answers

    What is the main function of drugs that act to depress cardiac activities, such as quinidine?

    <p>They reduce heart rate during arrhythmias.</p> Signup and view all the answers

    Which mechanism does activated charcoal utilize to impact the cellular environment?

    <p>Absorption of toxic chemicals.</p> Signup and view all the answers

    What effect do drugs that alter osmotic pressure typically have on cells?

    <p>They cause cell swelling or dehydration.</p> Signup and view all the answers

    What role do receptors play in drug interactions within a cell?

    <p>They recognize and initiate responses to drug signal molecules.</p> Signup and view all the answers

    Which of the following classes of drugs is known to act on renal glucose reabsorption?

    <p>SGLT2 inhibitors.</p> Signup and view all the answers

    How do drugs bind to receptors according to the lock and key model?

    <p>They must have a shape that closely fits the receptor's structure.</p> Signup and view all the answers

    What does the intensity of a drug response depend on?

    <p>The fit of the drug molecule to the receptor and the number of receptors occupied.</p> Signup and view all the answers

    Which type of bond is generally associated with drugs that have a long duration of action?

    <p>Covalent bonds.</p> Signup and view all the answers

    What is a defining characteristic of a receptor in cellular signaling?

    <p>It recognizes specific signal molecules but has no inherent function.</p> Signup and view all the answers

    Which of the following statements about drug-receptor interactions is incorrect?

    <p>Drug-receptor interactions do not affect biochemical systems.</p> Signup and view all the answers

    What is primarily affected when a drug interacts with its receptor?

    <p>Cellular metabolism and activity can be altered.</p> Signup and view all the answers

    What is the relationship between drug potency and the amount needed to produce a pharmacological response?

    <p>Higher potency requires smaller amounts of the drug.</p> Signup and view all the answers

    Which parameter is NOT evaluated in a time-response curve?

    <p>Rate of metabolism</p> Signup and view all the answers

    What is the purpose of achieving plasma concentrations between the MEC and MTC?

    <p>To maximize the therapeutic benefits while minimizing toxicity</p> Signup and view all the answers

    Which statement best defines Minimum Effective Concentration (MEC)?

    <p>The lowest plasma concentration required for therapeutic effect</p> Signup and view all the answers

    What does the therapeutic window represent?

    <p>The concentration range for achieving therapeutic effects without toxicity</p> Signup and view all the answers

    What nursing consideration is essential when administering drugs with a narrow therapeutic window?

    <p>Carefully check the dose and rate of administration to avoid toxicity</p> Signup and view all the answers

    If the plasma level of a drug decreases below the MEC, what is the likely outcome?

    <p>Adequate drug dosing is not achieved</p> Signup and view all the answers

    How are Minimum Toxic Concentration (MTC) and Minimum Effective Concentration (MEC) related?

    <p>MEC indicates the threshold for therapeutic effects, while MTC indicates toxicity.</p> Signup and view all the answers

    What does the position of the dose-response curve on the x-axis indicate about a drug's potency?

    <p>A curve closer to zero indicates higher potency.</p> Signup and view all the answers

    How is maximal efficacy defined in pharmacology?

    <p>The largest effect a drug can produce when all receptors are occupied.</p> Signup and view all the answers

    Which of the following factors does efficacy depend on?

    <p>Number of drug-receptor complexes formed.</p> Signup and view all the answers

    What common misconception do people have regarding the term 'potent' in pharmacology?

    <p>It refers exclusively to a drug's effectiveness without regard to dosage.</p> Signup and view all the answers

    Which description accurately represents cell membrane-embedded enzyme receptors?

    <p>The drug binding activates the enzyme located inside the cell.</p> Signup and view all the answers

    Which receptor family allows ions to flow into and out of cells upon activation?

    <p>Ligand-gated ion channels.</p> Signup and view all the answers

    Which of the following statements is true regarding the relationship between potency and efficacy?

    <p>Potency has no impact on efficacy measures.</p> Signup and view all the answers

    What does the ligand-binding domain refer to?

    <p>The specific site on the receptor where drugs bind.</p> Signup and view all the answers

    What is the primary characteristic of an antagonist?

    <p>It inhibits the action of an agonist.</p> Signup and view all the answers

    What distinguishes competitive antagonism from non-competitive antagonism?

    <p>Competitive antagonists prevent maximum agonist activity by blocking the active site.</p> Signup and view all the answers

    Which drug is specifically known as an opioid antagonist used to counteract morphine toxicity?

    <p>Naloxone</p> Signup and view all the answers

    What is the definition of selective toxicity in pharmacology?

    <p>The ability of a drug to target only specific pathogen systems.</p> Signup and view all the answers

    What effect do agonists typically have on receptors over time?

    <p>They tend to desensitize the receptor's response.</p> Signup and view all the answers

    Which of the following pairs exemplifies competitive antagonism?

    <p>Acetylcholine and Atropine</p> Signup and view all the answers

    How does a non-competitive antagonist affect the agonist's action?

    <p>It alters the receptor so the agonist cannot bind effectively.</p> Signup and view all the answers

    What differentiates a partial agonist from a full agonist?

    <p>A partial agonist has lower intrinsic activity than a full agonist.</p> Signup and view all the answers

    Study Notes

    Introduction to Pharmacodynamics

    • Pharmacodynamics is the study of the biochemical and physiological effects of drugs on the body and the molecular mechanisms by which those effects are produced.
    • It is the study of what drugs do to the body and how they do it.
    • Drug-induced changes in normal physiologic functions are explained by the principles of pharmacodynamics.

    Objectives

    • Understand the general concept of pharmacodynamics
    • Explain the principles of drug action
    • Understand the role of receptors in drug action and response
    • Define some pharmacodynamic terms
    • Discuss the relevance of pharmacodynamics to professional nursing practice
    • Employ the pharmacodynamics of drugs to improve benefits and minimize risks

    Benefits of Pharmacodynamics

    • Nurses need a basic understanding of pharmacodynamics to participate rationally in achieving therapeutic objectives.
    • Nurses must know about drug actions to educate patients and make decisions about drug use, as well as evaluate patients for beneficial and harmful drug effects.
    • Nurses need to understand drug actions when conferring with prescribers regarding drug therapy.

    Mechanisms of Drug Action

    • There are two main mechanisms of drug action:
      • Alteration in cellular environment (non-receptor mediated)
      • Alteration in cellular function (receptor mediated)

    Alteration in Cellular Environment

    • Some drug actions change the cellular environment physically or chemically.
    • Examples include changes in osmotic pressure (e.g., mannitol), lubrication (e.g., liquid paraffin), absorption (e.g., activated charcoal), or conditions on the cell membrane.
    • Examples of drug actions include mannitol which changes osmotic pressure in brain cells and reducing cerebral edema. Liquid paraffin, arachis oil, docusate are examples of drugs changing cellular environment through lubrication. Activated charcoal is an example of a drug acting by altering absorption.

    Alteration in Cellular Function

    • Most drug actions alter an intrinsic physiological process rather than creating a new process.
    • Drugs which alter cellular function can increase or decrease certain physiological functions, such as heart rate, blood pressure, GI motility, or urine output.

    Targets of Drug Action

    • Majority of drugs interact with target biomolecules:
      • Enzymes
      • Ion channels
      • Transporters
      • Receptors (usually a protein)

    Enzymes as Drug Targets

    • Almost all biological reactions are catalyzed by enzymes, making them major drug targets.
    • Drugs can increase or decrease enzyme-mediated reactions.
    • Enzyme inhibition is the most common mode of drug action.

    Ion Channels

    • Some drugs affect specific ion channels to exert pharmacological action by activating (opening) or inactivating (closing) channels.
    • Examples include calcium channel blockers (e.g., nifedipine, amlodipine), diuretics (e.g., furosemide), and anesthetic agents (e.g., lidocaine).

    Transporters

    • Drugs can either enhance or inhibit the activity of carrier/transport proteins.
    • Examples include calcitriol for calcium and phosphate absorption, and monoamine reuptake inhibitors (e.g., SSRIs, TCAs) affecting neurotransmitter reuptake. SGLT2 inhibitors are used for diabetes and heart failure treatment.

    Drug Receptors

    • A receptor is a reactive site, macromolecule or binding site on the surface or inside of a cell.
    • It recognizes signal molecules (drugs) and initiates a response, but itself does not have a function.
    • Drug receptors are typically proteins or glycoproteins often found on cell membranes.
    • The interaction between a drug and receptor site affects biochemical processes in the cell, causing changes in cellular activity, membrane permeability, or metabolism.
    • Drug fit to a receptor is like a key fitting to a lock. The closer the shape, the better the fit, and the better the therapeutic response.
    • Drug response intensity is related to how good the fit of the drug molecule and the number of receptor sites occupied.

    Drug-Receptor Complex

    • The pharmacophore is the part of the drug molecule that binds to the receptor.
    • The auxophore are the parts of the drug molecule that are not directly involved with binding.

    Drug Receptor Interaction

    • Drug-receptor interaction is the binding of the drug molecule to a reactive site on a cell or tissue surface.
    • A pharmacologic response is produced when a drug binds and interacts with its receptor.

    Drug Receptor Interactions: Affinity

    • Affinity is the measure of the strength of binding between a drug and its receptor.
    • Higher affinity means a faster and stronger binding.
    • Affinity is evaluated by the dissociation constant (KD). A smaller KD means a higher affinity.

    Drug Receptor Interactions: Efficacy

    • Efficacy is the relationship between receptor occupancy and the ability of the drug to initiate a response at the cellular, tissue or system level.
    • Efficacy is how well an action is taken after the drug binds to its receptor.
    • A high efficacy indicates a good outcome after the drug action.

    Drug Receptor Interactions: Potency

    • Potency refers to the drug activity in terms of the amount needed to produce an effect.
    • A highly potent drug elicits a given response with low concentrations.
    • Potency depends on both affinity and efficacy.

    Dose-Response Curves

    • Dose-response curves illustrate the effect of varying drug concentrations on receptors.
    • The curve shows the dose on the X-axis and the measured effect on the Y-axis.

    Onset, Peak, and Duration of Action

    • Onset of action: The time taken for a drug to reach its minimum effective concentration (MEC).
    • Peak action: The point at which the drug effect is highest.
    • Duration of action: The length of time the drug has a pharmacologic effect.

    Basic Terminologies

    • Minimum Effective Concentration (MEC): The lowest drug concentration that produces a desired pharmacologic response.
    • Minimum Effective Dose: The minimum dose of a drug needed to produce a therapeutic effect.
    • Minimum Toxic Concentration (MTC): The lowest drug concentration that produces toxic effects.
      • Therapeutic Window: The range between the MEC and MTC.
      • Wider therapeutic window = safer drug dosing.

    Assignment

    • Discuss Therapeutic Index.
      • The formula for measuring Therapeutic Index.
      • How does therapeutic index relate to the safety of drugs (low/high therapeutic index)?
    • Nursing considerations when administering drugs with a low therapeutic index.

    Drug-Receptor Interactions

    • There are four receptor families: Cell membrane-embedded enzymes, Ligand-gated ion channels, G-protein-coupled receptor systems, and Transcription factors.
    • The ligand-binding domain is the site where drugs bind to receptors.

    Drug-Receptor Interactions

    • Receptors have an excellent ability to recognize and bind ligands (drugs).
    • Binding can cause changes in the receptor which leads to a cellular response.

    Drug-Receptor Interactions: Types

    • Cell membrane-embedded enzymes: Drug binding activates enzymes within the cell leading to a response.
    • Ligand-gated ion channels: Binding opens/closes channels affecting ions flow into/out of the cell (e.g., sodium, calcium).
    • G-protein-coupled receptor systems: Involves a receptor, a G protein, and an effector which is either an enzyme or ion channel.
    • Transcription factors: Proteins binding to DNA in the nucleus which affects gene transcription, activation (response) is prolonged.

    Drug-Receptor Interactions: Agonists and Antagonists

    • Agonists: Drugs that combine with receptors to activate them causing an effect.
    • Antagonists: Drugs that combine with receptors without activation, blocking the agonist's effect.
    • Partial agonists: Produce a sub-maximal response even when all receptors are occupied.

    Receptor Theory

    • Receptor theory explains drug behavior/action in the presence of accurate knowledge of receptors.
      • Receptor Occupancy theory (A.J. Clark): Drug response is proportional to the number of receptors occupied. The response ceases when the complex dissociates.
      • Rate theory (Paton): drug effect is proportional to the rate of drug-receptor complex formation.

    Other Drug Receptor Theories

    • There are other theories like Induced-Fit, Macromolecular Perturbation, Activation Aggregation, and Two State Receptor Models.

    Combined Effects of Drugs

    • Synergism: Combined effect is greater than the sum of individual effects.
    • Additive effect: Combined effect equals the sum of individual effects.
    • Supra-additive effect: Combined effect is greater than the sum of individual effects.

    Drug Receptor Interaction: Intrinsic Activity

    • Intrinsic Activity is the ability of a drug to elicit a response after binding to a receptor.

    Drug Effects on Receptors

    • Agonist: Binds to and activates receptor. Key fits the lock, opening the door to a response.
    • Partial agonist: Binds, activates, but elicits only a submaximal response, even with all the receptors occupied.
    • Antagonist: Binds, but does NOT activate the receptor, blocking the agonist from activating.

    Types of Drug Antagonism

    • Competitive antagonism: Antagonist binds to the same site as agonist, reducing the agonist's affinity and potency. Higher doses of the agonist can reverse the antagonist's effect.
    • Non-competitive antagonism: Antagonist binds to a different site than the agonist, changing the receptor's shape so the agonist can no longer bind. Higher agonist doses do not overcome the effect of the antagonist.

    Selective Toxicity

    • Ideal chemotherapeutic agents target specific enzyme systems in pathogens or diseased cells without affecting healthy cells.
    • Penicillin acts as an example of selective toxicity, specifically targeting bacteria.

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