Pharmacology Course Overview: PK and PD Principles

Compartmental models simplify the body into compartments representing tissues with similar blood flow and drug affinity, helping to understand drug distribution and elimination.

The central compartment represents well-perfused organs like the heart, brain, and liver, while the peripheral compartment represents less highly-perfused tissues such as muscle, fat, and bones.

With first-order kinetics, the rate of drug elimination is directly proportional to the amount of drug present in the body. This means that as the drug concentration decreases, the elimination rate also decreases.

<p>The elimination half-life is the time it takes for the drug concentration in the body to decrease by half. This is a constant value for a drug, meaning each half-life takes the same amount of time, regardless of the initial concentration.</p> Signup and view all the answers

<p>The fraction of dose remaining in the body at time 't' provides information about how quickly the drug is eliminated and helps determine how long the drug's effects will last. It helps predict drug concentration over time.</p> Signup and view all the answers

<p>The one-compartment model assumes that the entire body behaves as a single, homogenous unit with a uniform drug concentration. This implies that drug distribution and elimination occur at the same rate throughout.</p> Signup and view all the answers

<p>Linear kinetics means that the rate of drug elimination is proportional to the drug concentration in the body. This means that the elimination process remains consistent regardless of the drug concentration.</p> Signup and view all the answers

<p>With first-order elimination, the body can handle increasing drug burdens efficiently. The rate of elimination increases proportionally to the drug load, allowing the body to eliminate the drug faster.</p> Signup and view all the answers

<p>Intravascular and extravascular.</p> Signup and view all the answers

<p>Local exposure targets a specific area, like eye drops for the eye or topical cream for the skin, while systemic exposure involves drug distribution throughout the body, reaching various organs via the bloodstream.</p> Signup and view all the answers

<p>Oral (swallowing), transdermal (applying to the skin), intramuscular (injection into muscle).</p> Signup and view all the answers

<p>Plasma and blood.</p> Signup and view all the answers

<p>Changes in blood/plasma drug concentration reflect changes in drug concentrations in tissues. This is because the drug is distributed throughout the body and reaches different tissues, leading to changes in concentration in specific tissues as the concentration in the blood/plasma changes. Consequently, monitoring blood/plasma drug concentration provides valuable insight into its distribution and effectiveness within various tissues.</p> Signup and view all the answers

<p>Unbound drug represents the free portion of the drug in circulation that can interact with target sites and exert its pharmacological effect. Bound drug is the portion attached to plasma proteins, such as albumin, which limits its availability for action.</p> Signup and view all the answers

<p>The two main types of biological matrices used in pharmacokinetic studies are invasive and non-invasive.</p> Signup and view all the answers

<p>Three non-invasive matrices used in PK studies include: 1. Urine: Provides a good indication of overall drug excretion. 2. Saliva: Allows for non-invasive sampling, often reflecting free drug concentration. 3. Breath: Can be used to measure volatile substances and the drug's rate of elimination. Non-invasive matrices are preferred because they are less invasive, easier to collect, and often provide a good indication of systemic drug exposure.</p> Signup and view all the answers

<p>Drug concentration measurements help determine the absorption, distribution, metabolism, and elimination (ADME) of a drug in the body, providing information about its pharmacokinetic profile.</p> Signup and view all the answers

<p>Factors that influence drug distribution include blood flow, tissue permeability, and protein binding.</p> Signup and view all the answers

<p>The protein-bound fraction of a drug cannot freely distribute to tissues and is considered pharmacologically inactive. Therefore, it is important to account for this fraction when assessing the drug's effectiveness and duration of action. Only the unbound fraction is available to interact with target receptors and exert its therapeutic effects.</p> Signup and view all the answers

<p>One scenario where biological matrix choice impacts interpretation is the analysis of lipid-soluble drugs. A drug that accumulates in fat tissue may have a significantly higher concentration in a tissue sample compared to a blood sample, providing a misleading picture of its systemic availability. Therefore, choosing the appropriate matrix, like blood or plasma, can better reflect the drug's overall distribution and efficacy in the body.</p> Signup and view all the answers

<p>Understanding the pharmacokinetic profile allows healthcare professionals to adjust drug dosages, select appropriate administration routes, and monitor drug efficacy and safety in individual patients.</p> Signup and view all the answers

<p>The elimination half-life (t1/2) represents the time it takes for the concentration of a drug in the body to decrease by 50%. For example, if a drug has a half-life of 3 hours, after 3 hours, the concentration of the drug in the body will be reduced to half of its initial amount.</p> Signup and view all the answers

<p>The elimination half-life (t1/2) is inversely proportional to the elimination rate constant (k). A higher elimination rate constant (k) means a faster rate of drug elimination, which leads to a shorter half-life. Conversely, a lower elimination rate constant (k) implies a slower elimination rate and a longer half-life.</p> Signup and view all the answers

<p>The elimination half-life is crucial for understanding drug behavior in the body. First, it determines the time required for drug concentrations to reach therapeutic levels. Second, it guides the development of appropriate dosing regimens and intervals to maintain effective drug levels while minimizing side effects.</p> Signup and view all the answers

<p>18 hours.</p> Signup and view all the answers

<p>The rate of change in the amount of drug in the body is proportional to the amount of drug present at any given time, with the proportionality constant being the elimination rate constant, k.</p> Signup and view all the answers

<p>Drugs with shorter half-lives require more frequent dosing to maintain therapeutic levels, while drugs with longer half-lives can be administered less frequently. This difference affects the convenience and effectiveness of treatments, and clinicians must choose regimens accordingly.</p> Signup and view all the answers

<p>C0 represents the initial concentration of the drug in the body, i.e., the concentration of drug in the body immediately after intravenous bolus administration.</p> Signup and view all the answers

<p>The elimination half-life can be determined experimentally by measuring drug concentrations in blood or plasma at different time points after drug administration. The data is then plotted on a graph, and the time taken for the concentration to decrease by half is measured, representing the half-life.</p> Signup and view all the answers

<p>The elimination rate constant, k, and the half-life of the drug are inversely proportional. A higher k means a faster elimination rate and a shorter half-life.</p> Signup and view all the answers

<p>$t_{1/2} = ln(2)/k$</p> Signup and view all the answers

<p>The elimination half-life provides an estimate of how long a drug will remain effective in the body. For example, a drug with a short half-life might be used for quick relief, while a drug with a long half-life might be used for chronic conditions, requiring less frequent dosing.</p> Signup and view all the answers

<p>The equation <code>ln C = -kt + ln C0</code> represents a linear relationship between the natural logarithm of the drug concentration (ln C) and time (t). The slope of this linear relationship is equal to the negative of the elimination rate constant, k.</p> Signup and view all the answers

<p>The equation <code>A = A0 * e^-kt</code> describes the exponential decay of the amount of drug in the body over time. A0 is the initial amount of drug in the body, and k is the elimination rate constant.</p> Signup and view all the answers

<p>The volume of distribution, V, is the theoretical volume that the drug appears to occupy in the body, based on its concentration. It is calculated as <code>V = A/C</code>, where A is the amount of drug in the body and C is the concentration of drug.</p> Signup and view all the answers

<p>The initial amount of drug, A0, is equal to the product of the initial concentration of drug, C0, and the volume of distribution, V: <code>A0 = C0 * V</code>.</p> Signup and view all the answers

<p>This equation shows that plotting the natural logarithm of the drug concentration (ln C) against time (t) will result in a linear relationship with a slope of <code>-k/2.303</code>, where k is the elimination rate constant. This relationship is used for graphically determining the elimination rate constant from experimental data.</p> Signup and view all the answers

<p>The rate of drug elimination is directly proportional to the amount of drug present in the body. This means that as the amount of drug decreases, the rate of elimination also decreases.</p> Signup and view all the answers

<p>The elimination rate constant (k) represents the fraction of drug eliminated per unit time. It determines the speed at which a drug is removed from the body.</p> Signup and view all the answers

<p>The elimination rate constant (k) is a constant value that represents the fraction of drug eliminated per unit time, while the rate of elimination (-dA/dt) is a variable that changes over time based on the amount of drug present. The rate of elimination is the actual speed at which the drug is being removed from the body at a specific moment while k describes the general speed of elimination.</p> Signup and view all the answers

<p>Drug elimination follows first-order kinetics, meaning the rate of elimination is directly proportional to the amount of drug present. As the drug is eliminated, the amount decreases, leading to a slower elimination rate.</p> Signup and view all the answers

<p>The rate of elimination would be 10 mg/hr (-dA/dt = k*A = 0.2 hr-1 * 50 mg = 10 mg/hr).</p> Signup and view all the answers

Refers to locations like blood/plasma where drug concentrations are assessed.

Drugs that are attached to proteins in the blood, limiting their availability.

Drugs that are not attached to proteins, available for action in the body.

Different substances like plasma, blood, and urine used to study pharmacokinetics.

Variations in blood/plasma drug levels that indicate changes in tissue levels.

A constant that defines the rate of drug elimination from the body.

A type of drug elimination where the rate is proportional to the concentration of the drug.

The change in drug amount (A) over time, reflecting how quickly it is eliminated.

An equation that shows the relationship between the elimination rate and drug amount.

Another name for the elimination rate constant, emphasizing its proportionate nature.

Models that represent the body as compartments for drug distribution.

The compartment consisting of blood and well-perfused organs.

The compartment for less highly-perfused tissues.

A measure of how quickly a drug is eliminated from the body.

The time it takes for the drug concentration to reduce by half.

A simplification where the body is treated as a single compartment for drugs.

A type of kinetics where the drug concentration relates directly to the rate of elimination.

Methods by which drugs are introduced into the body, including intravenous and extravascular routes.

A drug administration route that directly introduces substances into the bloodstream.

Drug administration routes that do not enter the bloodstream directly, using organs like the GI tract or lungs.

Drug administration aimed at a specific area, resulting in localized effect without systemic distribution.

Drug effects that occur throughout the body after entering systemic circulation.

Evaluating the levels of drug in biological matrices like blood or plasma, distinguishing between bound and unbound forms.

Bound drugs are attached to proteins in the blood, while unbound drugs are free to exert effects.

Pharmacokinetics referring to the concentration of drug in the bloodstream following a rapid intravenous injection.

A rapid injection of a drug directly into the bloodstream.

A decrease in drug concentration that follows an exponential pattern.

The speed at which drug concentration decreases in the body.

The mathematical process used to express drug amount as a function of time.

A logarithm that is useful for exponentially decreasing values in kinetics.

Replacing drug amount (A) with a concentration and volume relationship.

The steepness in a graph indicating the rate of drug elimination (k).

The time for plasma drug concentration to decrease by half.

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

The total amount of drug present in the body at any time.

Elimination rate depends on the drug's concentration level.

A rapid decrease describes how drug concentration diminishes over time.

A logarithm used in pharmacokinetic equations to simplify calculations.

C = C0 * e^(-kt), relating drug amount and time.