Introduction to Pharmacokinetics
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Questions and Answers

What does pharmacodynamics study?

  • The rate of drug excretion from the body
  • The mechanism of action of drugs (correct)
  • The distribution of drugs within the bloodstream
  • The absorption of drugs in the body

Which of the following components is NOT part of pharmacokinetics?

  • Distribution
  • Receptors (correct)
  • Metabolism
  • Excretion

Why is understanding pharmacokinetics important for drug administration?

  • It ensures the effective timing and frequency of dosages. (correct)
  • It evaluates patient’s psychological responses to drugs.
  • It reduces the chances of allergic reactions.
  • It helps in determining drug cost-effectiveness.

What does the acronym ADME stand for in pharmacokinetics?

<p>Absorption, Distribution, Metabolism, Excretion (B)</p> Signup and view all the answers

How is digoxin, used for treating heart failure, best administered for maximum effect?

<p>Once daily (D)</p> Signup and view all the answers

What is the primary mechanism by which most drugs are absorbed across epithelial cells?

<p>Simple diffusion (A)</p> Signup and view all the answers

Which type of drugs is absorbed more effectively in the stomach?

<p>Acidic drugs (B)</p> Signup and view all the answers

What is a significant characteristic of carrier-mediated transport for drug absorption?

<p>It requires energy (A)</p> Signup and view all the answers

Basic drugs are excreted faster in which type of urine?

<p>Acidic urine (B)</p> Signup and view all the answers

What role do tight junctions in epithelial cells play in drug absorption?

<p>They limit the passage of hydrophilic drugs (D)</p> Signup and view all the answers

Which of the following drugs would likely not be absorbed effectively when reaching the kidneys due to its ionization?

<p>Aspirin (B)</p> Signup and view all the answers

What factor contributes to a drug's absorption in the small intestine rather than the stomach?

<p>Increased surface area in the small intestine (A)</p> Signup and view all the answers

Which drug property is NOT mentioned as a factor affecting drug absorption?

<p>Molecular weight (B)</p> Signup and view all the answers

Which patient condition may negatively impact the absorptive surface and therefore drug absorption?

<p>Celiac disease (B)</p> Signup and view all the answers

What is a characteristic of highly polar drugs regarding their absorption route?

<p>They cannot be effectively administered orally. (C)</p> Signup and view all the answers

How does a 50% decrease in the volume of distribution affect the half-life of a drug?

<p>The half-life will decrease. (C)</p> Signup and view all the answers

What is a key difference between IV injection and oral administration of the same drug dose?

<p>IV injection skips the absorption phase. (C)</p> Signup and view all the answers

How long does it typically take for a drug administered orally to reach steady state plasma concentration compared to continuous infusion?

<p>Longer for oral than for continuous infusion. (C)</p> Signup and view all the answers

In a two-compartment model, what does the alpha-phase typically represent?

<p>Distribution of drug into the tissues. (D)</p> Signup and view all the answers

What happens to steady state plasma concentration when a drug eliminated via zero-order kinetics is doubled?

<p>It doubles. (B)</p> Signup and view all the answers

Which pharmacokinetic factor is affected by the drug's route of administration?

<p>All of the above. (D)</p> Signup and view all the answers

Which factors determine the appropriate route of drug administration?

<p>Patient-related and drug-related factors. (A)</p> Signup and view all the answers

What is a primary focus of studying pharmacokinetics?

<p>Monitoring drug absorption and elimination. (B)</p> Signup and view all the answers

Which drug is commonly administered sublingually for rapid action in emergency cases?

<p>Glyceryl trinitrate (B)</p> Signup and view all the answers

Which route of drug administration involves injecting a drug into the subcutaneous fat?

<p>Subcutaneous (B)</p> Signup and view all the answers

What is the most common muscle used for intramuscular injections?

<p>Deltoid (A)</p> Signup and view all the answers

Which of these statements about oral drug administration is true?

<p>Most drugs taken orally can have delayed effects. (C)</p> Signup and view all the answers

What angle should be maintained when administering an intramuscular injection?

<p>90 degrees (D)</p> Signup and view all the answers

Which medication is often injected intramuscularly for immediate effect?

<p>Morphine (C)</p> Signup and view all the answers

During a subcutaneous injection, what potential complication should be monitored for?

<p>Abscess formation (A)</p> Signup and view all the answers

Which route allows for the fastest onset of action among the following options?

<p>Intravenous (D)</p> Signup and view all the answers

What is the primary reason for administering Tab.Propranolol with food?

<p>To reduce the risk of gastrointestinal irritation (D)</p> Signup and view all the answers

Why is there a difference in the dose of Propranolol when administered orally versus intravenously?

<p>Intravenous administration delivers the drug directly into circulation, requiring a lower dose (A)</p> Signup and view all the answers

Which of the following factors significantly influences the bioavailability of a drug?

<p>Chemical structure of the drug (A)</p> Signup and view all the answers

What is one primary mechanism of how lipophilic drug molecules cross cell membranes?

<p>Passive diffusion through the lipid bilayer (C)</p> Signup and view all the answers

What distinguishes phase I reactions from phase II reactions in drug metabolism?

<p>Phase I introduces functional groups, while phase II involves conjugation with larger molecules (D)</p> Signup and view all the answers

Which parameter is expressed in units of clearance related to drug elimination?

<p>Volume per time, usually in mL/min (D)</p> Signup and view all the answers

Which route of administration generally has the highest bioavailability?

<p>Intravenous (A)</p> Signup and view all the answers

How does pH influence drug permeability across cell membranes?

<p>It alters the ionization state of the drug (B)</p> Signup and view all the answers

Flashcards

Highly Polar Drugs

Drugs that remain ionized (charged) in the body, making them poorly absorbed orally.

Drug Absorption in Small Intestine

The small intestine is the primary site for drug absorption due to its large surface area, which increases contact with the drug.

Drug Absorption: Lipid Solubility

Drugs that are more lipid-soluble (fat-soluble) are absorbed more easily into the bloodstream.

Drug Ionization

The process of a drug gaining or losing a charge, making it more or less likely to be absorbed.

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Factors Affecting Drug Absorption

Drug absorption can vary depending on factors related to the drug itself, the patient's health, and the site of administration.

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Pharmacology

The study of drugs and their effects on the body.

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Pharmacodynamics

The study of how drugs interact with the body and produce their effects.

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Pharmacokinetics

The study of how the body processes a drug, including its absorption, distribution, metabolism, and excretion.

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ADME

The four processes of pharmacokinetics: Absorption, Distribution, Metabolism, and Excretion.

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Why study pharmacokinetics?

Understanding pharmacokinetics helps us administer drugs effectively and predict their impact on the body.

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Drug Absorption

The process by which a drug enters the bloodstream from the site of administration. Different routes of administration, like oral, intravenous, or subcutaneous, lead to different absorption rates.

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Factors affecting absorption

Characteristics of the drug (e.g., solubility, size, pH) and the patient (e.g., gastric emptying rate, blood flow) influence the rate of absorption.

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Drug Distribution

Once absorbed, the drug travels throughout the body to its target sites. Distribution is influenced by factors like blood flow, protein binding, and tissue permeability.

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Drug Metabolism

The body's process of breaking down drugs into smaller, more easily excretable forms. The liver is the primary site of metabolism.

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Drug Excretion

The elimination of drug metabolites from the body, primarily through the kidneys in urine. The rate of excretion influences the duration of drug action.

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Bioavailability

The fraction of a drug that reaches the systemic circulation after administration. It's different for various routes of administration.

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Drug Clearance

The volume of blood that is cleared of the drug per unit time. It's a measure of how efficiently the drug is removed from the body.

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Half-Life Change with Volume of Distribution

If a drug's volume of distribution suddenly decreases by 50%, its half-life will also be reduced by 50%.

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IV vs. Oral Administration - Pharmacokinetic Differences

IV injection delivers the drug directly into the bloodstream, resulting in rapid absorption and peak plasma concentration. Oral administration involves absorption through the gut, leading to slower absorption and lower peak concentration.

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Time to Reach Steady State - Oral vs. Continuous

Oral administration requires multiple doses to reach steady state, while continuous infusion achieves it faster due to a constant drug input.

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Two-Compartment Model - Graphical Representation

A two-compartment model shows drug concentration over time with an initial rapid decline (alpha-phase) followed by a slower decline (beta-phase).

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Alpha-Phase in Two-Compartment Model - What does it represent?

The alpha-phase represents the distribution of the drug from the central compartment (bloodstream) to the peripheral compartment (tissues).

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Steady State with Dose Doubling - Zero-Order Kinetics

If a drug is eliminated via zero-order kinetics, doubling the dose will double the steady state plasma concentration.

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Steady State with Dose Doubling - First-Order Kinetics

If a drug is eliminated via first-order kinetics, doubling the dose will increase the steady state plasma concentration but not double it.

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Pharmacokinetics - Definition

Pharmacokinetics is the study of how the body handles a drug over time. It involves the processes of absorption, distribution, metabolism, and excretion.

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Simple Diffusion

Movement of drugs across cell membranes from high to low concentration, without needing energy or a carrier. This is the most common way drugs cross membranes.

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Carrier-Mediated Transport

Drugs use specific protein carriers to cross cell membranes. This process can be selective and requires energy.

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pH and Ionization

The acidity (pH) of the environment affects how easily drugs are absorbed. Acidic drugs are better absorbed in acidic environments like the stomach, while basic drugs are better absorbed in basic environments like the intestines.

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Drug Absorption: Location

Different body parts absorb drugs better depending on their structure. Tight junctions in epithelial cells, kidney filtration, and the jejunum of the small intestine are key absorption sites.

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Clinical Implication: Drug Excretion

The pH of urine affects how quickly drugs are excreted. Acidic drugs are excreted faster in alkaline urine, while basic drugs are excreted faster in acidic urine.

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Sublingual Route

Drug placed under the tongue, absorbed through the buccal membrane, used in emergency cases. Example: Glyceryl trinitrate for acute angina.

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Intramuscular Injection (I.M.)

Drug injected into a skeletal muscle. Common sites: Gluteus maximus, deltoid, rectus femoris, triceps. Faster action than oral, but slower than intravenous.

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Subcutaneous Injection (S.C.)

Drug injected into the subcutaneous fat layer. Common sites: Abdomen, thigh. Used for slow and sustained drug release. Example: Insulin injections.

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Intravenous Injection (I.V.)

Drug directly injected into a vein, bypassing absorption. Fastest route for immediate action.

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Oral Route

The most common route of drug administration. Drug is swallowed and absorbed in the small intestine. Slower action than other routes.

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Parenteral Routes

Drug administration methods that bypass the digestive tract, such as injections. Faster action than oral route.

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Reconstitution

Adding a liquid (usually sterile water) to a powder drug to create a solution ready for administration.

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Common Sites for I.M. Injections

Gluteus maximus, deltoid, rectus femoris, triceps. Choose the site based on the drug, patient's condition & volume.

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Study Notes

Introduction to Pharmacokinatics

  • Pharmacokinectics is the study of drug movement in the body
  • It involves the processes of absorption, distribution, metabolism, and excretion (ADME)
  • Pharmacodynamics is the study of the drug's mechanism of action on the body

Principles of Pharmacokinectics

  • Drugs are administered differently due to pharmacokinetics
  • Digoxin (heart failure) is better administered once daily
  • Paracetamol (fever) is typically given 3-4 times a day
  • Insulin (diabetes) is less effective when administered orally

Learning Objectives

  • Define pharmacokinectics
  • Describe the principal mechanisms of drug movement in the body
  • Explain how drug molecules cross cell membranes
  • Identify the main routes of drug administration
  • Determine drug bioavailability
  • Explain drug metabolism and excretion
  • Discuss drug clearance and half-life
  • Describe how drug administration affects concentration versus time

Routes of Drug Administration

  • Oral route: Drugs taken by mouth, absorbed in the small intestine
  • Inhalation route: Drugs inhaled into the lungs
  • Topical route: Drugs applied to the skin or mucous membranes
  • Rectal route: Drugs inserted into the rectum
  • Parenteral route: Drugs injected (intravenous, intramuscular, subcutaneous, intradermal)

Drug Absorption

  • Movement of drug from administration to systemic circulation
  • Depends on chemical nature of drug
  • Ionization and pH influence drug absorption
  • Lipid solubility determines drug crossing cell membranes

Drug Distribution

  • Reversible transfer of drug between the blood and extra-vascular fluids (tissues)
  • Factors affecting distribution: degree of ionization, lipid solubility
  • Drugs can be concentrated in specific tissues

Plasma Protein Binding

  • Acidic drugs bind to albumin, basic drugs to glycoprotein
  • Prolongs drug availability (reservoir effect)
  • Drug displacement interactions can occur

Bioavailability

  • Fraction of drug absorbed and entering systemic circulation unchanged
  • Affected by administration route and other factors

First-Pass Metabolism

  • Metabolism of drug in the liver before reaching systemic circulation is affected by the route of administration
  • Some drugs experience significant first-pass metabolism

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Description

This quiz focuses on pharmacokinetics, the study of drug movement within the body, covering essential processes such as absorption, distribution, metabolism, and excretion (ADME). You'll learn about drug administration routes, bioavailability, and how various factors affect drug concentration over time. Test your understanding of key principles and mechanisms governing how drugs operate in the body.

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