Biopharmaceutics/Pharmacokinetics Lecture 1

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Questions and Answers

Which phase directly precedes the pharmacokinetic phase?

  • Drug-target interaction phase
  • Pharmacodynamic phase
  • Pharmacological availability phase
  • Pharmaceutical phase (correct)

Which of the following best describes the main focus of biopharmaceutics?

  • The measurement of drug concentrations in biological fluids.
  • The correlation between a drug's physicochemical properties and its biological effects. (correct)
  • The investigation of how drugs are absorbed, distributed, metabolized, and excreted.
  • The study of drug-target interactions at the molecular level.

According to the content, what is an important aspect of the pharmaceutical phase?

  • Disintegration and Dissolution (correct)
  • Drug-receptor binding
  • Metabolism of the drug
  • Drug excretion from the body

Which of these is NOT explicitly identified as a factor influenced by biopharmaceutics?

<p>Drug binding at the receptor (A)</p> Signup and view all the answers

In the context of the chart presented, which process directly follows 'Pharmaceutical Availability'?

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

Which of these best describes the function of toxicokinetics?

<p>To apply pharmacokinetic principles to interpret toxicity data and extrapolate to humans. (A)</p> Signup and view all the answers

What is primarily being analyzed when studying pharmacodynamics?

<p>The relationship between drug concentration at the site of action and the pharmacologic response. (D)</p> Signup and view all the answers

Which of the options constitutes a non-invasive method for obtaining samples for drug concentration assays?

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

What does 'non-linear pharmacokinetics' at toxic doses most likely involve?

<p>Saturation of enzymes and other molecules involved in drug processes, such as metabolism (B)</p> Signup and view all the answers

Which analytical method is best suited for separating a drug from other substances in a biological sample?

<p>Chromatography, such as HPLC (D)</p> Signup and view all the answers

Which factor is NOT typically considered when evaluating formulation properties relevant to systemic absorption?

<p>Patient's age and gender (B)</p> Signup and view all the answers

The term 'kinetikos', as it relates to pharmacokinetics, primarily refers to the:

<p>Motion or movement of the drug (D)</p> Signup and view all the answers

In the context of pharmacokinetic parameters, what is the primary relationship between the rate constant for absorption and drug amount in the body?

<p>The rate constant influences the rate at which drug enters the body, thus affecting the amount of drug (B)</p> Signup and view all the answers

Which of these best describes a key focus of the experimental aspects of pharmacokinetics?

<p>Developing assays for drugs and their metabolites (D)</p> Signup and view all the answers

What is the primary goal of developing models in the theoretical aspects of pharmacokinetics?

<p>Predicting drug disposition following administration (C)</p> Signup and view all the answers

Therapeutic drug monitoring (TDM) is MOST critical for drugs that have a:

<p>Narrow therapeutic index (D)</p> Signup and view all the answers

Population pharmacokinetics focuses on studying variability in drug response due to:

<p>Age, gender, and ethnic factors (B)</p> Signup and view all the answers

Which of the following is the BEST description of how the different aspects of pharmacokinetics are interconnected?

<p>Experimental data informs theoretical modeling, which then guides clinical applications. (C)</p> Signup and view all the answers

What does the term supernatant refer to in the context of blood samples?

<p>The liquid portion of blood obtained after centrifuging. (D)</p> Signup and view all the answers

Which blood component is obtained after centrifuging coagulated whole blood?

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

What does the area under the curve (AUC) in a plasma concentration-time graph represent?

<p>Total drug exposure over time (D)</p> Signup and view all the answers

What is a primary use of the AUC in drug studies?

<p>Evaluation of toxicity and bioequivalence (A)</p> Signup and view all the answers

Why might whole blood samples be preferred over plasma or serum samples for drug assays in research settings?

<p>Whole blood contains all drug-related components, including bound cellular elements within. (A)</p> Signup and view all the answers

According to the provided text, which biological specimens are explicitly mentioned for drug concentration assays?

<p>Blood, serum and plasma (D)</p> Signup and view all the answers

Besides plasma concentrations, what other information is needed to make the most informed decisions about drug dosing?

<p>Other relevant pharmacokinetic information (C)</p> Signup and view all the answers

What is a key difference between using plasma versus serum in drug concentration assays?

<p>Plasma is obtained from non-coagulated blood unlike serum. (C)</p> Signup and view all the answers

Why is urine concentration an indirect indication of systemic drug concentration?

<p>Because it represents the cumulative excretion of the drug over time through the kidneys. (B)</p> Signup and view all the answers

What does fecal drug concentration primarily indicate?

<p>The degree of drug systemic absorption after oral administration or biliary excretion (D)</p> Signup and view all the answers

Why are saliva concentrations useful in drug monitoring?

<p>They approximate free drug concentrations in plasma because free drug can passively diffuse into saliva. (A)</p> Signup and view all the answers

What is a key function of a pharmacokinetic model?

<p>To use mathematical equations to optimize dosage regimens for individual patients. (A)</p> Signup and view all the answers

Which is NOT a factor that a pharmacokinetic parameter's value depends on?

<p>The individual's genetic predispositions. (C)</p> Signup and view all the answers

What is the significance of the pharmacokinetic parameter 'ke'?

<p>It reflects the rate at which a drug's concentration decreases. (D)</p> Signup and view all the answers

What does the pharmacokinetic parameter t1/2 represent?

<p>The time needed for half of the drug to be eliminated from the body. (A)</p> Signup and view all the answers

What is the role of INR measurement in patients taking anti-coagulants?

<p>It measures the blood's ability to clot. (C)</p> Signup and view all the answers

Which characteristic is unique to physiologically-based models when compared to compartment-based models?

<p>Reliance on actual anatomical and physiological data. (D)</p> Signup and view all the answers

In a mammillary model, what is the primary characteristic of the central compartment?

<p>It includes the plasma and highly perfused tissues such as liver and kidney. (A)</p> Signup and view all the answers

What is a key assumption of both mammillary and catenary compartment models?

<p>They assume an open system with drug entry and exit. (A)</p> Signup and view all the answers

Which of the following best explains how a catenary model differs from a mammillary model?

<p>A catenary model involves a central compartment that is sequentially connected to multiple tissue compartments, unlike a mammillary model. (C)</p> Signup and view all the answers

What is a ‘compartment’ in the context of pharmacokinetic compartment models?

<p>A tissue or tissue group that shares similar blood flow and drug affinity. (A)</p> Signup and view all the answers

In pharmacokinetic modeling, what is the primary purpose of using rate constants?

<p>To describe drug movement into and out of a compartment. (B)</p> Signup and view all the answers

What is a key limitation of using compartment-based models for extrapolation to different species?

<p>Their Volume of Distribution (Vd) has a limited relationship to blood flow and volume. (D)</p> Signup and view all the answers

In a one-compartment mammillary model following intravenous drug injection, where does drug elimination occur?

<p>Directly from the central compartment. (D)</p> Signup and view all the answers

Which type of model relies more on direct experimental data for parameters like blood flow and tissue volume?

<p>Physiologically-based models (A)</p> Signup and view all the answers

Which statement best reflects the impact of pathophysiological conditions on pharmacokinetic models?

<p>Both physiological and compartment models are influenced by pathophysiological conditions through data modification. (B)</p> Signup and view all the answers

Flashcards

Pharmacokinetics

The branch of pharmacology that focuses on how the body affects a drug, including absorption, distribution, metabolism, and excretion.

Biopharmaceutics

The study of how the physical and chemical properties of a drug influence its biological effects.

Drug Absorption

The process by which a drug enters the bloodstream from the site of administration.

Drug Distribution

The process by which a drug is distributed throughout the body.

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Drug Metabolism

The process by which a drug is broken down into inactive metabolites.

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Systemic Absorption

The process by which a drug enters the bloodstream from the site of administration.

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Pharmacokinetic Analysis

The mathematical analysis of how drug concentrations change over time in the body.

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Drug Dose

The amount of drug given to a patient.

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Absorption Rate

The rate at which a drug is absorbed into the body.

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Elimination Rate

The rate at which a drug is removed from the body.

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Pharmacodynamics

The study of how a drug affects the body.

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Drug Concentration

The amount of drug present in the body at a given time.

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Toxicokinetics

The study of how the body processes and eliminates drugs, including absorption, distribution, metabolism, and excretion.

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Drug Concentration Assays

Analyzing biological samples like blood, urine, or tissue to measure the concentration of a drug or its metabolites.

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Invasive Methods (Drug Concentration Assays)

Methods involving taking samples from inside the body, like blood draws or biopsies.

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Non-Invasive Methods (Drug Concentration Assays)

Methods for obtaining drug samples that don't involve invading the body, like saliva, urine, or breath analysis.

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Area Under the Curve (AUC)

Measures the amount of drug the body has been exposed to; used in toxicity and bioequivalence studies.

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Serum

The supernatant obtained after centrifuging coagulated whole blood, containing proteins and other components, but no blood cells.

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Plasma

The supernatant obtained after centrifuging non-coagulated whole blood, containing blood proteins and clotting factors, but no blood cells.

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Peak Concentration

The highest concentration of a drug in the blood after administration.

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Trough Concentration

The lowest concentration of a drug in the blood between doses.

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Half-Life (t1/2)

The time it takes for the drug concentration in the blood to reach half its peak level.

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Onset of Action

The time it takes for a drug to reach its desired effect.

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Pharmacokinetic Model

A model that uses mathematical equations to describe the relationship between drug concentration and time in the body. It helps predict future drug levels, optimize dosage, understand drug interactions, and evaluate bioequivalence.

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Pharmacokinetic Parameter

A constant value that characterizes a drug's behavior in the body, determined from experimental data. It helps understand a drug's distribution, elimination, and other properties.

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Tissue Biopsy

A small sample of tissue removed for diagnostic purposes. It can be used to analyze drug concentrations, but it has limitations regarding blood flow and drug distribution within the tissue.

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Urine Concentration

The concentration of a drug in urine, which reflects the overall drug level in the body. Not as precise as blood concentration, but useful for monitoring long-term drug therapy.

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Fecal Concentration

The concentration of a drug in feces, indicating lack of absorption after oral intake or removal via bile after reaching the blood.

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Saliva Concentration

The concentration of a drug in saliva, which reflects the free drug level in plasma. Useful for drugs that readily cross membranes and can provide insight into the body's overall drug exposure.

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Half-life

The time it takes for the concentration of a drug in the body to decrease by half. This helps determine how often medication should be given.

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Volume of Distribution (Vd)

The apparent volume of fluid that a drug is distributed into. This can be larger than the actual body volume since the drug may be concentrated in certain tissues.

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Physiologic Models

A type of pharmacokinetic model that uses actual anatomical and physiological data, like known tissue volumes, to simulate drug distribution in the body.

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Perfusion Models

These models assume a drug's distribution is based on perfusion, the blood flow to different tissues.

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Compartmental Models

A type of pharmacokinetic model that simplifies the body into compartments, each representing a group of tissues with similar blood flow and drug affinity.

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Mammillary Model

A compartmental model where the central compartment (plasma and highly perfused tissues) is connected to other compartments (tissues) like branches radiating outwards. A drug enters and exits the central compartment, with some transferring into peripheral tissues.

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Catenary Model

A compartmental model with multiple tissues connected in a chain-like structure, where a drug moves linearly from one tissue compartment to the next.

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Compartment Model Features

The compartmental model commonly used in pharmacokinetics, which assumes linear relationships between drug concentration and rate constants, and treats the body as an open system where drug can enter and leave.

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Physiologically Based Models

A model of drug distribution that uses complex, mathematical equations to predict concentrations based on physiological factors like tissue size, blood flow, and drug affinity.

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Model Contrast: Physiologically-based vs Compartmental

The compartmental model relies on fitting data to equations to predict drug concentrations, while physiologically based models directly simulate the physiological processes involved.

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Extrapolation: Compartmental Model

The compartmental model uses volume of distribution (Vd) as a theoretical construct, making it difficult to accurately extrapolate findings to different species.

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Extrapolation: Physiologically based Model

Physiologically based models can predict real tissue drug concentrations using data from multiple species, making extrapolation easier.

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Study Notes

Course Information

  • Course title: Biopharmaceutics/Pharmacokinetics
  • Course code: PSW 313
  • Instructor: Dr. G. Acquaah-Mensah
  • Lecture 1: Introduction to Biopharmaceutics and Pharmacokinetics

Course Objectives

  • Identify the place of pharmacokinetics in pharmacotherapy
  • Define terms related to pharmacokinetics, biopharmaceutics, and pharmacodynamics
  • Discuss various methods for analyzing biological samples
  • Explain models used in pharmacokinetics
  • Distinguish between different model types used in pharmacokinetics

Overview of Biopharmaceutics and Pharmacokinetics

  • Biopharmaceutics: The study of the relationship between the nature and intensity of biological effects and the physicochemical properties of a drug, also includes pharmacokinetics as a branch
  • Some key factors of interest in biopharmaceutics include: drug stability, drug release/dissolution rate-product, release rate-absorption site, and systemic absorption
  • Specific formulation properties of interest include: dosage form type, pharmaceutical processes utilized in preparation, presence or absence of excipients, physical state, particle size and surface area, and chemical nature (e.g., salt, complex, ester)
  • Pharmacokinetics: The study of how the body handles/processes a drug, including drug absorption, distribution, metabolism, and excretion. It is also involved in drug administration, the time-course of distribution, and concentrations attained in different regions of the body
  • An important concept: the relationship between drug concentration and drug response. This relationship is crucial in determining therapeutic and toxic effects.

Parameters of Interest

  • Amount of drug administered
  • Rate constant for absorption
  • Amount of drug in the body
  • Rate constant for elimination
  • Amount of drug eliminated

Pharmacokinetics - Experimental Aspects

  • Biologic sampling techniques development
  • Assay methods for drugs and metabolites development
  • Data collection and manipulation techniques development

Pharmacokinetics - Theoretical Aspects

  • Drug disposition models after administration
  • Classical pharmacokinetics: model development and parameter estimation (e.g., equations for volume distribution, clearance)

Pharmacokinetics - Clinical Aspects

  • Patient-specific considerations for drug dosing
  • Optimized dosing strategies
  • Therapeutic drug monitoring (TDM) for drugs with narrow therapeutic indices
  • Population pharmacokinetics (age, gender, ethnicity, genetics)

Toxicokinetics

  • Applies pharmacokinetic principles to toxicology
  • Interprets pre-clinical toxicity data and extrapolates to humans
  • Non-linear pharmacokinetics at toxic doses (e.g., enzyme saturation)

Pharmacodynamics

  • Relationship between drug concentration at the site of action and the resulting pharmacologic response
  • Describes how the drug affects the body

Drug Concentration Assays

  • Biological specimens: Blood, plasma, serum, tissue, other body fluids and urine concentrations
  • Methods used to obtain these specimens (e.g., invasive vs non-invasive)
  • Assay types: Chromatography (HPLC), Immunoassays (e.g., fluorescence), Radioactive assays (e.g., TCA-RA), Mass Spectroscopy
  • Use of data obtained from drug concentration assays to analyze drug dosing outcomes, metabolite formation, and drug transport.

Plasma Concentration-Time Course

  • AUC (Area Under the Curve): A measure of the total drug exposure in a patient
  • AUC is useful in toxicity profile and bioequivalence studies
  • Factors influencing plasma concentration-time curves (pharmacokinetic and pharmacodynamic factors)

Drug Concentration Assays - Additional Information

  • Plasma concentrations: optimization of drug dosage, further investigation of the relevant pharmacokinetic factors, and pharmacodynamic response (e.g., INR for anticoagulants and ECG for cardiotonic drugs.)
  • Tissue concentrations (e.g., biopsies and disadvantages)
  • Urine and Fecal concentrations (e.g., indirect indication of systemic concentration, lack of absorption post-oral administration)
  • Saliva concentrations ( e.g., approximating free drug in plasma)

Pharmacokinetic Models - Introduction

  • Model types: Physiologically-based models, empirical (compartmental models))

Pharmacokinetic Models - Physiologic Models

  • Based on actual anatomical and physiological data
  • Blood flow and drug affinity
  • Tissue volume considerations
  • Examples of application: blood flow models or perfusion models

Pharmacokinetic Models - Compartment Models

  • Compartments: tissues or tissue groups with similar blood flow and drug affinity
  • Categories: Mammillary Model, Two-compartment system
  • Types: Linear assumptions; rate constants; open systems; estimates for concentrations in other compartments

Comparison of Physiologic and Compartment Models

  • Contrast of predictive capabilities in different scenarios and conditions, and when using animal data for human estimations (e.g., extrapolations

Model Types Contrasts

  • Physiologic vs. Compartmental Models - characteristics and comparisons. (e.g., data requirements, extrapolations)

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