Pharmacodynamics Flashcards
What is the difference between pharmacodynamics and pharmacokinetics?
Pharmacodynamics focuses on the effects of the drug on the body, such as receptor binding and physiological response, while pharmacokinetics examines how the body affects the drug through absorption, distribution, metabolism, and excretion (ADME).
What are receptors in pharmacodynamics?
Receptors are specific proteins on or within cells that drugs bind to in order to initiate a physiological response. Receptors determine the drug’s specificity and its effects, playing a critical role in pharmacodynamics.
What is a dose-response relationship?
A dose-response relationship describes how the drug’s effect changes with its concentration or dose. It is typically represented by a curve showing the increase in response with an increase in dose until reaching a maximum effect.
What are agonists and antagonists?
An agonist is a substance that binds to a receptor and activates it, causing a physiological response. An antagonist, on the other hand, binds to the receptor but blocks activation, preventing a response.
What is drug efficacy?
Drug efficacy is the maximum effect a drug can produce, regardless of dose. It represents the drug’s ability to achieve the desired therapeutic effect once it binds to its receptor.
What is potency in pharmacodynamics?
Potency refers to the amount of drug needed to produce a specific effect. A more potent drug requires a lower dose to achieve the same effect as a less potent drug.
How is the pA2 value determined, and what does it signify?
The 𝑝𝐴2 value is determined using the Schild equation:
log(DoseRatio−1)=log(AntagonistConcentration)−𝑝𝐴2
𝑝𝐴2 represents the negative log of the molar concentration of a competitive antagonist that requires doubling the agonist concentration to achieve the same effect, indicating the antagonist’s affinity for the receptor.
What are the four main stages of pharmacokinetics?
The four stages are Absorption, Distribution, Metabolism, and Excretion (ADME).
What is first-pass metabolism?
First-pass metabolism occurs when a drug is metabolized in the liver before it reaches systemic circulation, reducing its bioavailability.
What is the half-life of a drug?
The half-life is the time it takes for the concentration of a drug in the bloodstream to reduce by half.
What factors can affect drug absorption?
Factors include drug formulation, route of administration, blood flow to the site of absorption, lipid solubility, and pH of the environment.
What is the role of cytochrome P450 enzymes in drug metabolism?
Cytochrome P450 enzymes play a key role in the metabolism of many drugs, affecting their breakdown and clearance from the body.
What is drug-drug interaction in pharmacology?
Drug-drug interactions occur when two or more drugs are taken together, affecting the pharmacokinetics or pharmacodynamics of one or both drugs, leading to increased or decreased effects.
Why is the therapeutic window important in pharmacology?
The therapeutic window is the range between the minimum effective concentration and the minimum toxic concentration of a drug. It helps guide safe and effective dosing.
What are the effects of drug metabolism on drug activity?
Drug metabolism can activate a prodrug, inactivate an active drug, or alter the drug’s activity, influencing its therapeutic effect and duration of action.
What is the role of P-glycoprotein in pharmacology?
P-glycoprotein is an efflux transporter protein that pumps certain drugs out of cells, affecting their absorption, distribution, and elimination. It can lead to drug resistance by reducing drug effectiveness.
What is the mechanism of action of beta-blockers?
Beta-blockers block beta-adrenergic receptors, reducing heart rate, blood pressure, and myocardial oxygen demand.
What are the two phases of drug metabolism?
Phase I: Functionalization reactions (e.g., oxidation, reduction, hydrolysis).
Phase II: Conjugation reactions (e.g., glucuronidation, sulfation) to make drugs more water-soluble for excretion.
What is receptor occupancy theory?
Receptor occupancy theory states that the magnitude of a drug’s effect is proportional to the number of receptors occupied, up to a maximum effect when all receptors are occupied.
What are the factors that influence drug-receptor binding?
Factors include drug concentration, affinity, receptor density, and competitive interactions with other molecules.
How do you find the antagonist concentration causing a twofold shift in EC₅₀?
Interpolate between the data for antagonist concentrations.
For example, if EC₅₀ is 10 nM at “zero A” and 30 nM at “10 nM A,” estimate the antagonist concentration for a 20 nM EC₅₀.
What does a higher pD₂ value indicate?
A higher pD₂ value indicates a more potent agonist, as a lower concentration is needed to cause a twofold shift in EC₅₀.
How do you convert nM to M for pD₂ calculations?
Divide the concentration in nM by
10⁹ . For example, 10 nM = 10 × 10⁻⁹ M = 1 × 10⁻⁸ M.
What does 𝑝𝐴2 represent in pharmacology?
𝑝𝐴2 is the negative logarithm of the molar concentration of an antagonist required to double the EC₅₀ of an agonist. It is a measure of antagonist potency in competitive inhibition.
