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PK EXAM 1
Terms in this set (83)
When drug clearance decreases, steady state plasma concentrations
Results in smaller fluctuations between peak and trough plasma levels
small doses very frequently
For a drug regimen, if the elimination rate constant (k) of a drug is reduced while Vd, Xo, and tau remain constant, the peak and trough concentration will
With a continuous IV infusion of drug, the steady-state plasma concentration is directly proportional to the
drug infusion rate
Steady state plasma concentration is approximately reached when the continuous infusion has been given for at least how many half lives of the drug?
Doubling the infusion rate of a drug will
increase the drug's steady state twofold
A decrease in drug dose will result in
lower plasma concentrations at steady state but will not change the time to reach steady state
A larger volume of distribution will result in the
same amount of drug distributing in a greater volume, which would result in lower peak-to-trough variation
The extent to which a drug is absorbed partially determines its
F is described as
the fraction of the administered drug that reaches the systemic circulation
Absorption of a drug from a tablet form involves
dissolution of the solid dosage form into GI fluids and diffusion though body fluids and membranes
Drugs are absorbed more quickly will reach a
higher peak concentration since less elimination has taken place
Anionic drugs and weak acids are more likely to bind to
Cationic drugs and weak bases are more likely to bind to
Disease states that alter drug distribution
renal, heart, liver
Factors that decrease plasma protein concentration
liver disease, trauma, surgery, burns, and renal disease
If unbound fraction of drug in plasma decreased what would happen to the Vd?
it would decrease
For drugs that do not distribute into adipose tissue well, Vd is based on
ideal body weight
Drug that is available to interact with receptors and/or enzymes and produce a pharmacological effect are
Drugs that are _____ can penetrate membranes and distribute extensively into fat tissue
Drugs that are _______ at physiological pH will not penetrate into fat tissue and will have a lower distribution
Only ______ drug can penetrate into tissues
Highly perfused tissues generally have higher drug distribution compared to _______ perfused tissues
For aminoglycosides, what must be calculated to estimate an individual patient's drug elimination rate?
Biotransformation is also known as
Biotransformation may be dependent on factors such as age, _______, and __________
disease and genetics
The liver receives its blood from the
portal vein and hepatic artery
The body converts a drug to a less active substance by a process called
Drug elimination encompasses both
metabolism and excretion
Significant first pass metabolism means that much of the drug's metabolism occurs before its arrival at the
A drug that is totally absorbed without any pre-systemic metabolism and undergoes hepatic extraction has what F equation
Because the extraction ratio can maximally be 1, the maximum value that hepatic clearance can approach is that of
hepatic blood flow
Hepatic elimination encompasses both the processes of
biotransformation and excretion
The basic functional unit of the liver is the
The liver receives blood supply from the GI tract via the
What type of metabolism do drugs with a high extraction ratio undergo to a significant extent?
Will drugs that inhibit the hepatic cytochrome P450 system likely increase or decrease the plasma clearance of theophylline?
What is NOT a phase I reaction?
Renal clearance can be calculated from the ratio of what rate to the drug's concentration plasma?
Two important routes of drug excretion are
renal and biliary
A patient with a history of smoking is likely to require higher or lower total daily dose of theophylline compared to a nonsmoker?
For aminoglycosides, the terminal elimination rate constant can be estimated from the creatinine clearance using what equation?
K=0.00293 hr-1 x (creatinine clearance) + 0.014
Glomerular filtration is a _________ process
Glucuronidation is a phase _____ biotransformation process
___________ is the maximal ability of the liver to eliminate drug in the absence of any blood flow limitations
What 3 factors should be considered when trying to access the effect of disease states on plasma concentrations of drugs eliminated by the liver
Route of administration, extraction ratio, and protein binding
A drug administered orally must go through the _______ before it is available to the systemic circulation
Tubular secretion most often occurs with
weak organic acids
When the rate of drug elimination proceeds at half the maximum rate, the drug concentration is known as
What drugs demonstrate nonlinear pharmacokinetics?
What equation describes the form of the Michaelis-Menton equation that relates daily drug dose to Vmax, KM, and the steady state plasma drug concentration?
daily dose= -KM (daily dose/C) + Vmax
What is used in the phenytoin injection vehicle that will precipitate with most IV fluids and is cardiotoxic (requiring a slow rate of infusion)?
Linear pharmacokinetics means that the AUC and plasma concentration achieved are directly related to the
size of the dose administered
At very low concentrations, drugs are more likely to exhibit
first order kinetics
At very high concentrations, drugs are more likely to exhibit
zero order kinetics, because enzymes are saturated
When hepatic metabolism becomes saturated there will be a disproportionate increase in the plasma concentration achieved because the amount of drug that can be eliminated over time can't _____
The most commonly used model in clinical pharmacokinetics
The amount of drug per unit of volume is
Instantaneous distribution to most body tissues and fluids is assumed in which model
EC50 refers to the drug concentration at which
one-half the maximum response is achieved
EC50 values can be used to compare the
potency of drugs in the same class
A drug that has first-order elimination and follows a one-compartment model, what plot would result in a straight line?
natural log of plasma concentration vs time
Describes predictable relationship between plasma concentration of a drug and the concentration of drug at the receptor where it produces therapeutic effect
relationship of drug concentrations to drug effect
study of the time course of drug absorption, distribution, metabolism, and excretion
Application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in an individual patient is
excretion, distribution, and metabolism
Increased drug metabolism that results in a decrease in the drug concentration and decreased drug absorption
Factors that cause variability in plasma drug concentrations after the same drug dose is given to different patients include variations in the
What would result in a drug having a high clearance?
High extraction ratio + high blood flow
Units for clearance are
Extensive binding to albumin, but not within or to blood cells, would have a concentration greater in the
Drugs that follow first order elimination, the amount of drug eliminated per unit of time
decreases while the fraction of drug eliminated remains constant
Measures the organ's ability to remove a drug
Body fluid compartments ranked from lowest to highest volume
plasma < extracellular fluid< intracellular fluid< total body water
If a drug is poorly distributed to tissues, its apparent volume of distribution is
Method of back extrapolation is used to calculate
the rate constant of drug elimination from the body
slope= - Beta
Definition of Beta
terminal elimination rate constant
Plasma drug concentration versus time curve for a two compartment model is represented by what type of curve?
With a two compartment model, the term K12 represents
rate constant for drug transfer from compartment 1 (central) to compartment 2 (peripheral)
In the two compartment model, Xp represents
amount of drug in the peripheral component
For a two compartment model, which is the term for the residual y-intercept for the terminal portion of the natural-log plasma concentration vs time line?
Large doses given at long dosing intervals will result in
great differences between maximum (peak) and minimum (trough) concentrations
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