Unit 2: Pharmacokinetic Parameters (Volume of Distribution) Flashcards
Time required for the concentration of a drug to decrease by one half
biologic half-life
Unit for biologic half-life
seconds, minutes, hours, etc.
Often related to its duration of action and also may indicate when another dose should be given
drug’s half-life
Determines the speed at which a drug is removed from the body
Elimination half-life/biologic half life
Sum of the rate constants for removal of drug from the body, including the rate constants for renal excretion and metabolism
Elimination rate constant
Is a first-order kinetic process, depending on -/ the overall elimination rate constant, k, and the amount of drug in the body, DB, remaining at any given time, t
Drug elimination
Represents the fraction of drug removed per unit of time
Elimination rate constant
Is elimination rate constant affected by route of administration?
No
Is elimination rate constant affected by physiologic or pathologic conditions of the patient (e.g. liver failure, age)
Yes
Unit for elimination rate constant
reciprocal time (sec-1, mins-1, hrs-1)
Reversible transfer of drug from one location to another within the body
drug distribution
Drug distribution to theoretical compartments
drug distribution
Most drugs ____(do not distribute uniformly/distribute uniformly)____ throughout the body but assumed that drug ___(does not uniformly/uniformly)___ distributes into a single compartment of fluid
do not uniformly; uniformly
Volume that must be considered in estimating the amount of drug in the body from the concentration of drug found in the sampling compartment
volume of distribution
Process of reversible transfer of a drug to and from the site of measurement, usually blood/plasma
volume of distribution
Fluid distribution in an adult
Interstitial fluid:
Plasma:
Intracellular fluid:
Extracellular fluid:
Total body water:
Interstitial fluid: 21%
Plasma:4%
Intracellular fluid: 35%
Extracellular fluid: 25%
Total body water: 60%
T/F
apparent volume of distribution (Vd) is of a true anatomic or physical value
F
Hypothetical volume of body fluid in which the drug is dissolved
apparent volume of distribution
Needed to estimate the amount of drug in the body relative to concentration of drug in the plasma
apparent volume of distribution
increase in Vd will result to an/a _____ in dose
increase
Reflects the amount of drug in the tissues, not in the plasma
apparent volume of distribution
Apparent volume of distribution reflects the amt of drug in the ______
tissues
Vd is _________ proportional in relation to the drug plasma concentration
inversely
Constant per any given drug
apparent volume of distribution
unit of apparent volume of distribution
volume (mL, L), % body weight
Apparent Volume of Distribution (Vd)
weight of 1 kg is assumed to be equal to _______
1-L volume
represents the dose of drug given by intravenous bolus (g, mg)
DB
represents the extrapolated drug concentration at zero time on the y-axis (mg/mL)
CP
inc blood flow = _____ Vd
inc
lipid soluble drugs = ____ Vd
inc
hydrophilic drug = _____ Vd
dec
unionized drug = ______ Vd
inc
higher body weight = ____ Vd
inc
elderly = _____ Vd
dec daw sabe sa ggl ???
A drugs which is more bound to plasma proteins than tissue proteins will ___ Cp and ___ Vd
inc; dec
A drug which has a high affinity for adipose tissues than plasma proteins will ___ Cp and ___ Vd
dec; inc
Vd of a lipophilic drug is ______ (large/small) in an obese patient
large
Vd is ______ (inversely/directly) proportional to the half-life
directly
Vd _____ (shortens/prolongs) half life = ______ (longer/shorter) DOA
prolongs; longer
Used for the computation of the loading dose of a drug
Vd
Determine or predict the distribution of drugs
Vd
Determines whether drug is predominantly in the plasma or in the body tissues
Vd
Compare the distribution characteristics of various drugs
Vd
