Podcast
Questions and Answers
What does a two-compartment model have in terms of characteristic half-lives?
What does a two-compartment model have in terms of characteristic half-lives?
- One half-life for both compartments
- Two half-lives, one for each compartment (correct)
- Three half-lives, one for each phase of elimination
- Half-life varies with the concentration in blood
Why might the elimination of a highly lipid-soluble substance from blood be rapid at first?
Why might the elimination of a highly lipid-soluble substance from blood be rapid at first?
- Due to high initial concentration in blood (correct)
- Due to rapid transfer from fat stores to blood
- The substance is eliminated in one phase
- Because the compound is not soluble in blood
In a plot of loge(concentration in blood) against time in a two-compartment model, what does the appearance of two straight line regions indicate?
In a plot of loge(concentration in blood) against time in a two-compartment model, what does the appearance of two straight line regions indicate?
- Changes in blood volume over time
- Fat stores releasing compounds into the blood
- Presence of two different substances in the blood
- Two different phases of elimination (correct)
How are the two half-lives determined in a two-compartment model?
How are the two half-lives determined in a two-compartment model?
What determines the kinetics of a toxic substance in a two-compartment model when the concentration in blood falls?
What determines the kinetics of a toxic substance in a two-compartment model when the concentration in blood falls?
How is the initial concentration estimated in each compartment in a two-compartment model?
How is the initial concentration estimated in each compartment in a two-compartment model?
What type of relationship is observed when plotting loge(concentration) against time in toxicokinetics?
What type of relationship is observed when plotting loge(concentration) against time in toxicokinetics?
Why are more detailed models like multiple compartment models necessary in toxicokinetics?
Why are more detailed models like multiple compartment models necessary in toxicokinetics?
Which compartments are involved in the toxicokinetic model depicted in Figure 3.9?
Which compartments are involved in the toxicokinetic model depicted in Figure 3.9?
When can partition coefficients be used in toxicokinetic models?
When can partition coefficients be used in toxicokinetic models?
In which scenario must the metabolic pathways and reaction kinetics be known in toxicokinetic modeling?
In which scenario must the metabolic pathways and reaction kinetics be known in toxicokinetic modeling?
What does the two straight line regions observed in a plot of loge(concentration) against time indicate?
What does the two straight line regions observed in a plot of loge(concentration) against time indicate?
What is the characteristic feature of substances exhibiting first order toxicokinetics?
What is the characteristic feature of substances exhibiting first order toxicokinetics?
In a first-order kinetic process, how much of the initial concentration remains after 3 half-lives?
In a first-order kinetic process, how much of the initial concentration remains after 3 half-lives?
Which type of kinetics is characterized by the concentration in tissues changing steadily with time?
Which type of kinetics is characterized by the concentration in tissues changing steadily with time?
What does the graph of the logarithm of concentration against time look like for substances with first-order kinetics?
What does the graph of the logarithm of concentration against time look like for substances with first-order kinetics?
What is another term for linear kinetics in toxicokinetics?
What is another term for linear kinetics in toxicokinetics?
In toxicokinetics, which substances have elimination rates proportional to their concentration in the body?
In toxicokinetics, which substances have elimination rates proportional to their concentration in the body?
Flashcards are hidden until you start studying
Study Notes
Toxicokinetics
- Toxicokinetics refers to the study of the rates of uptake and excretion of toxic substances in the body.
- Pharmacokinetics and toxicokinetics are essentially the same.
First Order Kinetics
- Most substances are eliminated at a rate proportional to their concentration in the body.
- The higher the concentration, the more rapid the elimination.
- Substances with first order kinetics have a characteristic half-life (t1/2).
- The initial concentration in the body falls to one half in 1 half-life, to 1/4 after 2 half-lives, 1/8 after 3 half-lives, and 1/16 after 4 half-lives.
Graph of Concentration vs. Time
- A graph of the logarithm of concentration of a substance in the body against time will be a straight line if the substance has first order single compartment kinetics.
- A two-compartment model may show two straight line regions, corresponding to the two phases of elimination.
Two-Compartment Model
- The two-compartment model involves the major body compartments, including the lungs, dermis, muscles, adipose tissue, white marrow, and liver.
- The model considers the rates of transport between compartments according to their capacities and blood perfusion rates.
- The model can be used if partition coefficients are known, but in other cases, metabolic pathways and reaction kinetics must also be known.
Elimination Curve
- The elimination curve for a toxic substance with two-compartment first order kinetics is a curve that asymptotically approaches zero.
- The perfusion for each compartment (in litres per minute) is an important factor in the model.
Half-Lives
- A two-compartment model has two characteristic half-lives, one for each compartment.
- The half-lives can be calculated from the slopes of the two straight line regions and extrapolated to estimate the initial concentration in each compartment.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
