EXAM 2 Reading (N.Ch6) Flashcards
The plasma half-life of a drug is inversely proportional to its
Rate of clearance
When you administer a bolus dose of a drug intravenously, which tissue would have an increase in the tissue concentration of the drug first?
Liver
The vessel-rich group,
which is comprised of the highly-perfused organs such as the brain, heart, liver, kidneys, lungs, and endocrine organs, receives 75% of the cardiac output.
They exhibit the most rapid equilibration of the drug with the blood (which group) ?.
The vessel-rich group
After distribution to the vessel-group, The drug then
redistributes to other, less-perfused tissues such as muscle, adipose tissue, and bone.
What is the most prevalent protein in the bloodstream?
Albumin
Which of the following plasma proteins binds preferably to acidic drugs?
Albumin is capable of binding drugs that are alkaline or neutral, but binds preferably to acidic drugs.
2 proteins that bind preferably to basic drugs.
Alpha-1 acid glycoprotein and Beta-globulin
Proteins that binds to corticosteroids.
Transcortin
Approximately what percent of the cardiac output goes to the adipose tissue group?
6%
The vessel-rich group receives ___%of the cardiac output.
75%
The muscle group receives about____% of the cardiac output
19%
The adipose group receives ____% of the cardiac output,
6%
Vessel-poor group receives a
% negligible proportion
Which of the following agents exemplifies zero-order kinetics?
Alcohol (ethanol)
Zero-order kinetics refers to metabolism in which
the amount of the drug eliminated over time is constant.
The clearance of a drug is inversely proportional to
its half-life
The clearance of a drug is defined as the C.
volume of plasma that is cleared of a drug per unit of time and is dependent upon the body’s ability to metabolize and eliminate the drug.
The formula for clearance is
Clearance = Q X E (where Q is blood flow and E is the extraction ratio).
Clearance is _____-(definition) - What does it mean?
directly proportional to the dose administered and inversely related to the half-life of the drug. Meaning, as the half-life of the drug increases, the volume that is cleared per unit of time decreases.
How does hypoalbuminemia affect the action of a highly protein-bound drug like warfarin?
Its effect is intensified
% of warfarin is protein-bound
About 98
As the plasma protein level decreases, there is
less of the protein available for the drug to bind with, and more of the free form of the drug is available to exert its pharmacologic action.
Hypoalbuminemia and highly protein bound drugs?
hypoalbuminemia intensifies the action of highly protein-bound drugs.
Which of the following statements are correct? (select two)
Plasma half life and zero-order kinetic
The plasma half-life of a drug is inversely proportional to its rate of clearance
A drug with zero-order kinetics exhibits a constant rate of elimination
Enzyme induction
reduces the plasma half-life of agents that are metabolized by that particular metabolic pathway.
According to the Fick equation, the most important factor in determining the rate of diffusion of a drug across a membrane is the
concentration gradient of the drug.
Membrane thickness is an important factor in the
rate of diffusion
Molecular weight, which affects the
diffusion coefficient (p)
Which of the following drugs will be more non-ionized than ionized at physiologic pH? (select two)
An acid with a pKa of 9.5
A base with a pKa of 4.2
For a WEAK ACID explain ph vs pka
pH < Pka –> Nonionized
pH > Pka –> Ionized
For a WEAK BASE explain ph vs pka
pH < Pka –> IOnized
pH > Pka –> NOn-Ionized
Which pharmacokinetic model best illustrates how lipid-soluble drugs are distributed?
Two-compartment model
For many drugs, a single-compartment model, which represents In
the distribution of the drug throughout the entire body sufficiently explains the pharmacokinetics of the drug.
For lipid-soluble drugs, however, what better illustrates how the drug is distributed?
two-compartment model better illustrates how the drug is distributed.
The peripheral compartment consists of the
muscles, adipose tissue, and bone
The two-compartment model, there is a central compartment, which consists of the
intravascular fluid and highly perfused tissues such as the heart, lungs, brain, kidneys, and live
Two-compartment membrane include the
Central and peripheral compartments
Immediately after administration of a bolus dose of a particular drug that undergoes first-order kinetics, you measure the plasma concentration, and it is 100 mcg/mL. The drug has an elimination half-life of 5 minutes. What would you expect the plasma concentration to be 15 minutes after the initial administration?
The elimination half-life of the drug is five minutes. The passing of 15 minutes would constitute three half-lives. With each half-life, the plasma concentration of the drug should drop by half. So, after the first five minutes, it would be 50 mcg/mL. After the second five minutes, it should be 25 mcg/mL. After the third five minutes, it should be 12.5 mcg/mL.
Which form of a drug is responsible for reaching the site of action?
Non-Ionized
In solution, the non-ionized form of a drug is considered to confer pharmacologic activity, because it is in then
non-ionized form that the drug is able to pass through lipid-soluble biologic membranes to reach its point of actio
Which term refers to the amount of the drug that is able to reach its target receptor after it is introduced into the circulatory system?
Bioavailability
A drug is being administered by continuous infusion, and its plasma concentration is now constant. The drug is said to be in
a steady state
Steady state refers to a .
stable plasma concentration of a drug.
With a single dose of a drug, the plasma concentration
increases as it is absorbed, reaches a peak plasma concentration, and then decreases as it is eliminated.With the chronic administration of a drug or a continuous infusion, however, the supply of the drug is continually renewed
Once the rate at which it becomes bioavailable equals the rate at which it is eliminated, the plasma concentration becomes
stable, and the drug is said to be at a steady state.
Presystemic elimination would be most likely to occur in a drug administered
Orally
Drugs administered orally may undergo_____What does it mean?
presystemic elimination. That is, they may be eliminated before they are able to reach the systemic circulation
What is the first-pass hepatic elimination.
The stomach acids may hydrolyze the drug, gastric enzymes can deactivate it, or it can be metabolized in the liver as it passes through the portal circulation before it reaches the systemic circulation, a process known as
The clearance of a drug is dependent upon (2)
blood flow and the Extraction ratio
There are also separate concepts of hepatic clearance and renal clearance that become important
when one or both organs has an alteration in either blood flow or the extraction ratio.
In pharmacokinetics, steady-state refers to a situation in which
the concentration of a drug in the tissues does not change from moment-to-moment
Steady-state refers to a state in which all of the tissues in the body have
had time to reach equilibrium.
Which route of administration requires a significantly higher dosage in most drugs to achieve a therapeutic plasma concentration?
Oral
Because of extensive first-pass metabolism, the oral dose of most drugs must be significantly
higher to generate therapeutic plasma concentrations.
The administration of lidocaine to a parturient can result in an increased concentration of the drug in the fetus. This concept that describes why this occurs is
ion trapping
Explain ion trapping?
When the lipid-soluble portion of a basic drug like lidocaine crosses the placenta and enters the acidic environment of the fetus, the drug becomes more ionized and unable to cross back through the placenta. As a result, a higher concentration of the drug exists in the fetus than in the mother. This concept is known as ion trapping.
The diffusion of a drug across a membrane from an area of higher concentration to an area of lower concentration without the expenditure of energy is
Passive Transport
Which of the following measurements predicts the time it takes for 50% of a drug to be eliminated from the central compartment when a continuous infusion is discontinued?
Context-sensitive half-time
The context-sensitive half-time predicts the time it takes for
50% of a drug to be eliminated from the central compartment when a continuous infusion is discontinued.
The volume of distribution describes the
virtual volume into which the drug is distributed.
The steady-state plasma concentration corresponds to the
steady concentration at the site of action and is determined by a concentration-response curve
It should be noted that context sensitive half-times are computer models that only
predict the time for 50% of the drug in the central compartment to be eliminated. It does not predict the time for recovery from the drug.
Which route of administration will produce a lower bioavailability of most drugs due to rapid metabolism in the liver via the first-pass effect?
Oral
Approximately how much of a drug will be remaining in the bloodstream after four elimination half-lives have passed for a drug that undergoes first-order kinetics?
5%
Which drug administration route would have the highest bioavailability?
IV
The intravenous route, by definition has __% bioavailability, has a
100% bioavailability because the entire dose of drug administered is available within the circulatory system immediately.
Intramuscular and subcutaneous administration both range between
75 and 100% bioavailability.
Routes such as oral, topical, and inhalation can vary widely depending on the chemical characteristics of the particular drug and how they affect its ability to be
absorbed into the bloodstream.
Hepatic enzyme induction will result in a reduction in the ____ of a drug.
Half life.
If liver enzymes are exposed to particular compounds or drugs over a period of time, they will
increase their activity, resulting in an increased ability to metabolize the drugs. This is referred to as hepatic enzyme induction, and it can result in a reduced half-life of a drug
The plasma half-life of a drug is directly proportional to its
Volume of distribution
Which is the single most important enzyme, accounting for 40-45 percent of all mediated drug metabolism?
CYP3A4
