43 Questions
What characterizes the disposition of the drug in the one compartment open model?
Monoexponential disposition with a linear plot of log concentration against time
What is the equation representing the steady-state of constant intravenous infusion in the one compartment open model?
$Ke \times XSS = K0$
What does the apparent volume of distribution (Vd) for a drug indicate in the one compartment open model?
It may be altered in certain pathological conditions or changes in body composition
What does constant intravenous infusion lead to in the one compartment open model?
The drug accumulating to reach a steady-state level
What does rapid intravenous injection result in according to the one compartment open model?
The entire dose of the drug entering the body immediately, distributing rapidly to all tissues
What characterizes the time course of a drug in the one compartment open model?
Dependent on initial concentration and elimination rate constant
What follows first-order kinetics in terms of elimination rate in the one compartment open model?
Rate of elimination
In a one compartment model, what does 'homogenous' mean?
Equilibrium between plasma and various tissues and fluids
What does the one compartment open model assume about drug concentration in plasma and other body tissues?
Proportional changes
What is the key characteristic of the one compartment open model?
Unidirectional absorption and elimination
Which statement best describes a compartment in the context of pharmacokinetics?
A tissue or group of tissues with similar blood flow and drug affinity
What does the term 'open' signify in the one compartment open model?
'Unidirectional' absorption and elimination of drug
What does the one compartment open model assume about changes in plasma levels of a drug?
'Proportional' changes in tissue drug levels
What is the equation representing the steady-state of constant intravenous infusion in the one compartment open model?
$Ke \times XSS = K0$
What does the apparent volume of distribution (Vd) for a drug indicate in the one compartment open model?
It indicates how extensively the drug is distributed in body tissues relative to the blood plasma.
What does constant intravenous infusion lead to in the one compartment open model?
It leads to the drug accumulating to reach a steady-state level.
What characterizes the disposition of the drug in the one compartment open model?
Monoexponential disposition with a linear plot of log concentration against time.
What does rapid intravenous injection result in according to the one compartment open model?
Immediate distribution of the entire dose to all tissues.
What follows first-order kinetics in terms of elimination rate in the one compartment open model?
The elimination rate constant - clearance - elimination half life
What does constant intravenous infusion involve in terms of input and reaching steady state?
Zero-order input with gradual attainment of steady state
What does 'homogenous' mean in a one compartment model?
Equal concentrations throughout all body tissues
What is primarily dependent on reaching steady-state drug concentration in terms of time?
The elimination half-life and clearance
What signifies 'open' in the one compartment open model?
Continuous influx and efflux of drug from tissues into plasma
What does the term 'homogenous' mean in the context of the one compartment open model?
Equilibrium between plasma and various tissues and fluids in the body
Which statement best characterizes the disposition of a drug in the one compartment open model?
Changes in plasma levels of a drug reflect proportional changes in tissue drug levels
What characterizes the time course of a drug in the one compartment open model?
Unidirectional absorption and elimination of the drug
In terms of elimination rate, what follows first-order kinetics in the one compartment open model?
$C = C_0 e^{-kt}$
What does constant intravenous infusion lead to in the one compartment open model?
$C_{ss} = \frac{Dose}{Cl \cdot \tau}$
What does rapid intravenous injection result in according to the one compartment open model?
Immediate distribution equilibrium followed by elimination
What does the apparent volume of distribution (Vd) for a drug indicate in the one compartment open model?
Extent of drug distribution throughout the body
Which statement best describes a compartment in the context of pharmacokinetics?
A tissue or group of tissues with similar blood flow and drug affinity
What is represented by 'ka' and 'ke' in the context of pharmacokinetics?
Rate constants for absorption and elimination processes, respectively
What characterizes the elimination phase in the one compartment open model?
First-order kinetics, elimination rate constant, elimination half-life, and clearance
What type of plot represents the disposition of a drug in the one compartment open model?
Monoexponential with a linear plot of log concentration against time
Which statement about constant intravenous infusion is true?
Ke * CSS = K0 represents the steady state in constant intravenous infusion
What is primarily dependent on the time required to reach steady-state drug concentration in constant intravenous infusion?
Elimination half-life
What happens if the infusion rate is increased in constant intravenous infusion?
A higher steady-state level is obtained without changing the time needed to reach steady state.
What does zero-order input involve in constant intravenous infusion?
The amount of drug in the body increasing gradually until it reaches a steady state or plateau.
What does constant intravenous infusion lead to at steady state?
The rate of change of the drug amount in the body being zero.
What is the equation representing the steady-state of constant intravenous infusion in the one compartment open model?
$C_{ss} = \frac{D}{Cl}$
What characterizes the disposition of the drug in the one compartment open model?
First-order elimination kinetics
What does rapid intravenous injection result in according to the one compartment open model?
Immediate attainment of steady-state concentration
What follows first-order kinetics in terms of elimination rate in the one compartment open model?
Dose-independent elimination process from plasma and tissues
Study Notes
One Compartment Open Model and Constant Intravenous Infusion
- The one compartment open model describes how a drug distributes in the body and is eliminated, with all accessible sites having the same distribution kinetics.
- The time course of a drug in this model depends on the initial concentration and elimination rate constant.
- Rapid intravenous injection results in the entire dose of the drug entering the body immediately, distributing rapidly to all tissues.
- The rate of elimination follows first-order kinetics, with the elimination rate constant, elimination half-life, and clearance characterizing the elimination phase.
- The disposition of the drug in this model is monoexponential, with a linear plot of log concentration against time.
- The apparent volume of distribution (Vd) for a drug is constant, but may be altered in certain pathological conditions or changes in body composition.
- Intravenous infusion at a zero-order rate offers advantages such as convenient administration, individualized regulation, and prevention of fluctuating blood levels.
- Constant intravenous infusion leads to the drug accumulating to reach a steady-state level, where the rate of drug leaving and entering the body are the same.
- The time required to reach steady-state drug concentration in the blood is primarily dependent on the elimination half-life.
- The model for constant intravenous infusion involves zero-order input, with the amount of drug in the body increasing gradually until it reaches a steady state or plateau.
- At the steady state, the rate of change of the drug amount in the body is zero, and the equation representing this state is Ke (elimination rate constant) multiplied by the steady-state concentration (XSS) equals the constant infusion rate (K0).
- If the infusion rate is increased, a higher steady-state level is obtained, but the time needed to reach steady state remains the same.
Test your knowledge of the one compartment model, which simplifies the body as a single, kinetically homogenous unit for drug distribution.
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