Disposition of Toxicants Flashcards
Biotransformation is vital in removing toxicants from the circulation. All of the following statements regarding biotransformation are true
- The liver is the most active organ in the biotransformation of toxicants.
- Water solubility is required in order for many toxicants to be excreted by the kidney.
- The kidney plays a major role in eliminating toxicants from the body.
- The lungs play a minor role in ridding the body of certain types of toxicants.
Active transport across cell membranes is
- Unlike simple or facilitated diffusion, active transport pumps chemicals against an electrochemical or concentration gradient.
- Unlike simple diffusion, there is a rate at which active transport becomes saturated and cannot move chemicals any faster.
- Active transport requires the expenditure of ATP in order to move chemicals against electrochemical or concentration gradients.
- Active transport exhibits a high level of specificity for the compounds that are being moved.
Might increase the toxicity of a toxicants administered orally?
increased dilution of the toxin dose.
most correctly describes the first-pass effect?
Orally administered toxicants are partially removed by the GI tract before they reach the systemic circulation.
important mechanism of removing particulate matter from the alveoli?
absorption into the bloodstream, followed by excretion via the kidneys.
For a toxicant to be absorbed through the skin, it must pass through multiple layers in order to reach the systemic circulation. Which of the following layers is the most important in slowing the rate of toxicant absorption through the skin?
stratum corneum
NOT an important site of toxicant storage in the body?
Muscle
The blood–brain barrier
The degree of lipid solubility is a primary determinant in whether or not a substance can cross the blood–brain barrier
Which of the following will result in DECREASED excretion of toxic compounds by the kidneys?
increased activity of the organic cation transporter.
Regarding the two-compartment model of classic toxicokinetics, what is true?
There is more than one dispositional phase.
Volume of distribution (Vd)
- Vd relates the total amount of chemical in the body to the concentration of chemical in the plasma.
- Vd is the apparent space into which an amount of chemical is distributed in the body to result in a given plasma concentration.
- A chemical that usually remains in the plasma has a low Vd.
- Vd can be used to estimate the
Chemical clearance
- In pharmacology, clearance is a pharmacokinetic measurement of the volume of plasma from which a substance is completely removed per unit time. Usually, clearance is measured in L/h or mL/min. The quantity reflects the rate of drug elimination divided by plasma concentration.
*is performed by multiple organs.
First-order elimination
*The rate of elimination is directly proportional to the amount of the chemical in the body.
* A semilogarithmic plot of plasma concentration versus time shows a linear relationship.
*Clearance is dosage independent.
*The plasma concentration and tissue concentration decrease similarly with respect to the elimination rate constant.
The toxicity of a chemical is dependent on the amount of chemical reaching the systemic circulation. Which of the following does influence systemic availability?
- Absorption after oral dosing
- hepatic first-pass effect.
- intestinal first-pass effect.
- incorporation into micelles
Advantage of a physiologically based toxicokinetic model?
- Complex dosing regimens are easily accommodated.
- The time course of distribution of chemicals to any organ is obtainable.
- The effects of changing physiologic parameters on tissue concentrations can be estimated.
- The same model can predict toxicokinetics of chemicals across species.
