Pharmacology IV Infusion Quiz
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Questions and Answers

What is the primary purpose of administering a loading dose before starting an IV infusion?

  • To maintain steady-state concentration immediately
  • To prolong the infusion time
  • To reduce side effects
  • To achieve a quick therapeutic concentration (correct)

    • The total drug concentration in plasma is the sum of only the IV bolus dose.

    False

    What is the formula for the concentration following IV bolus administration?

    C1 = Loading dose (DL)/Vd e-kt

    The loading dose DL can also be expressed as DL = _____.

    <p>R/K</p> Signup and view all the answers

    Match the following variables with their meanings:

    <p>DL = Loading Dose Css = Steady-state Concentration Vd = Volume of Distribution K = Elimination Rate Constant</p> Signup and view all the answers

    What does the term 'intravenous' mean?

    <p>Into the vein</p> Signup and view all the answers

    IV infusions started being developed significantly in the 1950s.

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

    What is one purpose of IV infusion?

    <p>To maintain stable plasma concentration</p> Signup and view all the answers

    IV solution may be given as a bolus dose or an ____________ infusion.

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

    Which of the following is NOT a benefit of using IV infusion?

    <p>Immediate post-operative pain relief</p> Signup and view all the answers

    Match the following characteristics with their respective terms:

    <p>Apparent volume of distribution = VD Elimination rate constant = k Drug distribution = Total tissue concentration IV bolus = Whole dose enters bloodstream directly</p> Signup and view all the answers

    What physiological processes are primarily responsible for drug elimination from the body?

    <p>Kidney and liver</p> Signup and view all the answers

    IV bolus administration delivers the entire dose of a drug slowly over time.

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

    What condition is reached when the rate of drug input equals the rate of drug output?

    <p>Steady-state</p> Signup and view all the answers

    At steady-state, the plasma drug concentration is directly related to the body clearance of the drug.

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

    What is the formula to calculate the elimination half-life (t½) of a drug?

    <p>T1/2 = 0.693 / k</p> Signup and view all the answers

    Css is defined as R / _____ .

    <p>VD.k</p> Signup and view all the answers

    If the infusion rate of a drug is 2 mg/hr and the serum concentration after 48 hours is 10 mg/L, what is the total body clearance (ClT)?

    <p>0.1 L/hr</p> Signup and view all the answers

    What is the observed elimination half-life of a drug given at an infusion rate of 15 mg/hr with plasma concentrations of 5.5 mg/L and 6.5 mg/L taken at 8 and 24 hours?

    <p>Approximately 8 hours</p> Signup and view all the answers

    At half the steady-state concentration, Cp is equal to Css/_____ .

    <p>2</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Css = Steady-state concentration of the drug t½ = Time required for the plasma concentration to decrease by half ClT = Total body clearance of the drug R = Rate of drug infusion</p> Signup and view all the answers

    What type of input process do drugs administered by constant IV infusion demonstrate?

    <p>Zero-order input process</p> Signup and view all the answers

    The rate of drug elimination during IV infusion is a zero-order process.

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

    What is the equation used to describe the rate of change in the amount of drug in the body during IV infusion?

    <p>dDB/dt = R - kDB</p> Signup and view all the answers

    At steady-state, the equation Css = R / ______ represents the concentration of the drug in the plasma.

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

    Match the parameters related to IV drug infusion with their definitions.

    <p>R = Rate of drug input k = Elimination rate constant DB = Amount of drug in the body Css = Steady-state concentration of the drug</p> Signup and view all the answers

    What happens to drug concentration when the IV infusion stops?

    <p>It declines according to first-order rate kinetics.</p> Signup and view all the answers

    The plasma drug concentration decreases to zero right after the infusion stops.

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

    Calculate the necessary infusion rate if the half-life of theophylline is 4 hours, the desired Css is 15 mg/L, and Vd is 25 liters.

    <p>63.75 mg/hr</p> Signup and view all the answers

    Study Notes

    IV Infusion

    • IV infusion involves administering drugs intravenously at a constant rate over a specific time interval.
    • Intravenous refers to "into the vein".
    • Infusion is a slow injection of a substance into a vein.

    Learning Objectives

    • Students will be able to define IV infusion.
    • Students will be able to understand the history of IV infusion.
    • Students will be able to explain the purpose for intravenous therapy.
    • Students will be able to explain the different types of intravenous fluids (IV bolus and infusion).
    • Students will be able to calculate the flow rate for an infusion.
    • Students will be able to identify the advantages of IV infusion.

    History of IV Infusion

    • IV technology originated from cholera treatment studies in 1831.
    • IV techniques further developed in the 1930s but became widely available in the 1950s.

    Purpose of IV Infusion

    • Maintain stable plasma concentration.
    • Avoid periods of low drug concentration.
    • Dosage adjustments
    • Maintain or replace body stores.
    • Restore acid-base balance.
    • Administer medication.
    • Provide nutrition.

    IV Solution Administration Types

    • Bolus dose.
    • Infused slowly into the plasma at a constant or zero-order rate.

    Intravenous Bolus Administration

    • IV bolus drugs enter the bloodstream directly.
    • Distribution of the drug occurs throughout the body tissues.
    • Drug concentration in tissues depends on blood flow, molecular weight, lipophilicity, plasma protein binding, and binding affinity with the tissue.
    • Drugs are mostly eliminated by the kidneys and/or liver after metabolism.

    Pharmacokinetic Parameters

    • Apparent volume of distribution (VD) is the first pharmacokinetic parameter.
    • VD represents the volume where the drug is distributed within the body.
    • Elimination rate constant (k) is the second pharmacokinetic parameter.
    • k governs the rate at which drug concentration declines over time.

    IV Infusion Calculation

    • IV(dose)—-> DB, Vd----->K---------> Elimination

    IV Infusion Considerations

    • High precision is achieved by infusing drugs intravenously as a drip.
    • The body is considered a single, kinetically homogeneous unit.
    • This route is applicable only for drugs that rapidly distribute throughout the body.
    • Drugs move dynamically within this compartment

    Zero-order Input Process

    • Drugs administered by constant IV infusion undergo a zero-order input process.
    • During this process, the drug enters the bloodstream at a constant rate.
    • Drug elimination is typically a first-order process for most drugs.
    • The rate of input minus the rate of output represents the change in drug amount within the body(dDB/dt).
    • A steady-state level is reached, where the rate of drug input equals the rate of drug output.

    Steady-State Equation

    • dDB/dt = R - k DB
    • R is the rate of drug input (infusion rate) and k is the elimination rate constant.
    • Cp = R/Vd K

    Steady State Considerations

    • At steady-state the rate of drug input (R) equals the rate of drug output (k DB).
    • R = k. DB and R = k .Cp .Vd
    • Cp=R/Vd.K
    • At steady-state, Cp = Css
    • Css = R/k.VD
    • Css = R/Cl
    • Once infusion stops, or when a steady-state has been reached, the drug concentration declines according to first order kinetics.
    • This decline will have a slope on the elimination curve equal to k/2.3.

    Example Calculation

    • A desired steady-state theophylline plasma concentration of 15 mg/L is needed.
    • The average half-life of theophylline is 4 hours and the apparent volume of distribution is 25 liters.
    • To calculate the rate of infusion needed to reach this concentration, the equation R = k . Css. VD must be used
    • R = 0.17/hr x 15 x 25
    • R = 63. 75 mg/hr

    Steady-State Drug Concentration

    • During drug administration, the plasma drug concentration increases and the elimination rate also increases.
    • The rate of elimination is concentration-dependent.
    • Cp keeps increasing until a steady-state condition is reached where drug input (IV infusion rate) equals drug output (elimination rate)

    Steady-state Drug Concentration Continued

    • At steady-state, the resulting plasma drug concentration is directly related to the rate of infusion and inversely related to the body clearance of the drug.
    • The therapeutic activity is observed when the drug concentration is close to the desired plasma concentration - the required steady-state drug concentration.

    Time to Reach Steady-State

    • The time to reach steady-state can be determined from the time taken to reach half the steady state concentration.

    • Css = R/VD.k = R/Clearance

    • At (t½); time to reach half the steady-state, Cp = Css/2

    • Cp = [R/Vd K] (1−e−kt half) = Css/2

    • taking the natural log on both sides

    • T1/2 = 0.693/k

    Additional Example

    • A patient with septicemia was administered IV infusion of an antibiotic that had an elimination half-life of 6 hours.
    • The infusion rate was 2 mg/hr.
    • After 48 hours, the serum drug concentration was 10 mg/L.
    • The problem requires determining overall body clearance for the drug.

    Calculating Patient Elimination Half-life

    • The half-life can be calculated from a mathematical expression that describes the elimination rate constant.
    • Cp =[ R/Vd K ] ( 1-e-kt)

    Additional Example

    • A patient is given an IV infusion of a specific antibiotic at 15 mg/hr.
    • The concentration is measured at 8 and 24 hr with a reading of 5.5 and 6.5 mg/L respectively.
    • The elimination half-life is calculated using the following equations.

    Loading Dose plus IV Infusion

    • To quickly achieve a therapeutic concentration, a loading dose of drug using rapid intravenous injection is followed by a slower maintenance dose
    • At this condition, the total drug concentration is dependent on IV bolus (dose) and the infusion dose.
    • The concentration using a IV bolus is described using:
    • C1 = Loading Dose (DL) / Vd x e^-kt=Coe^-kt
    • The concentration using IV infusion at infusion rate R is :
      • C2= [R/ Vd. K] (1-e^-kt)
    • The total concentration is sum of bolus and infusion: Cp= C1+C2

    Loading Dose and Steady State

    • If the loading dose represents the amount of drug in the body at steady-state(DL) then DL=Css.Vd, since Css=R/k.Vd.
    • Therefore, DL=R/K

    Example Calculation

    • A certain anesthetic drug is administered using IV infusion at a rate of 2 mg/hr, has an elimination rate constant of 0.1/hour and a volume of distribution(Vd) of 10L
    • The physician wants a drug level of 2 ug/mL right away
    • DL=Css.Vd= 2ug/mL x 10 L x 1000= 20mg.Alternatively DL=R/K=2/0.1=20mg

    Advantages of IV Infusion

    • Immediate therapeutic effect due to rapid drug/fluid delivery to target sites.
    • Applicable when patients cannot tolerate oral drugs.
    • Reduces pain and irritation from drugs administered intramuscular/subcutaneously.

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    Iv Infusion PDF

    Description

    Test your knowledge on the pharmacology of intravenous (IV) infusions and bolus administrations. This quiz covers concepts such as loading doses, drug concentration, and the benefits and mechanisms of IV therapy. It's designed for students and professionals looking to deepen their understanding of IV medication administration.

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