38 Questions
What type of pharmacokinetics is exhibited when a drug follows linear pharmacokinetics?
Linear pharmacokinetics
If a patient has a steady-state drug concentration of 10 μg/mL at a dosage rate of 100 mg/h, what will be the steady-state serum concentration if the dosage rate is increased to 150 mg/h?
15 μg/mL
What term is used to describe the situation when drug concentrations do not change proportionally with dose?
Nonlinear pharmacokinetics
What is the likely explanation when steady-state concentrations increase more than expected after a dosage increase?
Saturable or Michaelis-Menten pharmacokinetics
Name two drugs that follow Michaelis-Menten pharmacokinetics.
Phenytoin and salicylic acid
When steady-state concentrations increase less than expected after a dosage increase, what are two typical explanations?
Incomplete absorption or decreased bioavailability
Why does warfarin have a small volume of distribution?
It is highly bound to serum albumin.
Why does Digoxin have a large volume of distribution?
It is highly bound to tissues, primarily muscle.
What is half-life in pharmacokinetics?
Time required for serum concentrations to decrease by one-half after absorption and distribution phases are complete.
What is the elimination rate constant (ke) used to denote?
How quickly drug serum concentrations decline in a patient.
How are half-life and elimination rate constant related?
t1/2 = 0.693/ke
Why is half-life important in pharmacokinetics?
It determines the time to reach steady state during continuous dosing and the dosage interval.
What is the dimension for the elimination rate constant (ke)?
Reciprocal time (hour−1, minute−1, day−1, etc.)
What is the elimination phase of the drug concentration curve?
The terminal slope of the serum concentration/time curve after absorption and distribution phases are complete.
What happens to steady-state serum concentrations when drugs like valproic acid and disopyramide saturate protein binding sites?
Increase less than expected
How do drugs like carbamazepine affect their own rate of metabolism as the dose is increased?
Increase their own rate of metabolism (autoinduction)
What is the formula to calculate maintenance dose (MD) based on clearance (Cl) and steady-state serum concentration (Css)?
MD = Css ⋅ Cl
What does the term 'therapeutic range' refer to in pharmacology?
Range of steady-state concentrations that produce desired effects without adverse effects
What is the generally accepted therapeutic range for theophylline in the treatment of asthma?
10–20 μg/mL
Why is clearance (Cl) considered the most important pharmacokinetic parameter?
Determines the maintenance dose required for a given steady-state serum concentration
How does knowledge of a drug's clearance help in determining the required maintenance dose?
Easy to compute the required maintenance dose
What concentrations of theophylline are considered a reasonable starting point within the therapeutic range for asthma treatment?
8–12 μg/mL
What is the purpose of calculating the volume of distribution (V) for a drug?
The volume of distribution determines the loading dose required to achieve a desired steady-state drug concentration immediately after administration.
If 100 mg of a drug is administered to two patients with different volumes of distribution, how will the resulting serum concentrations differ?
The patient with a smaller volume of distribution will have a higher serum concentration compared to the patient with a larger volume of distribution.
Provide an example of a drug with a very small volume of distribution and explain why it has a small V.
Warfarin has a very small volume of distribution of 5-7 L because it is primarily contained in the blood and does not distribute widely in the body tissues.
Provide an example of a drug with a very large volume of distribution and explain why it has a large V.
Digoxin has a very large volume of distribution of 500 L because it distributes widely in the body and binds extensively to bodily tissues.
What is the relationship between a drug's binding in the blood or serum compared to its binding in tissues, and its volume of distribution?
The extent to which a drug binds in the blood or serum compared to its binding in tissues is an important determinant of its volume of distribution.
If a drug has a large volume of distribution, what does it imply about the loading dose required to achieve a desired steady-state concentration?
If a drug has a large volume of distribution, a larger loading dose will be required to achieve a desired steady-state concentration.
Explain the significance of the volume of distribution parameter in the context of drug dosing and achieving therapeutic drug levels.
The volume of distribution is a crucial parameter in determining the appropriate loading dose to rapidly achieve the desired steady-state drug concentration, which is essential for effective and safe drug therapy.
How would the volume of distribution differ for a drug that is highly lipophilic compared to a drug that is hydrophilic?
A highly lipophilic (fat-soluble) drug would generally have a larger volume of distribution compared to a hydrophilic (water-soluble) drug because lipophilic drugs can distribute more extensively into fatty tissues.
What is the difference between pharmacokinetics and pharmacodynamics?
Pharmacokinetics is what the body does to the drug, while pharmacodynamics is what the drug does to the body.
What is the significance of the term "volume of distribution" in calculating a drug loading dose?
The volume of distribution is used to calculate the loading dose of a drug needed to achieve a target concentration.
Explain the concept of "steady state" in clinical pharmacokinetics.
Steady state is the condition where the rate of drug administration equals the rate of drug removal, and the amount of drug in the body reaches a constant value.
How does steady state serum or blood concentrations relate to assessing patient response and computing new dosage regimens?
Steady-state drug concentrations are used to assess patient response and compute new dosage regimens, as they represent the equilibrium condition where drug levels are constant.
Explain the difference between linear and nonlinear pharmacokinetics.
In linear pharmacokinetics, drug concentrations increase proportionally with the dose, while in nonlinear pharmacokinetics, drug concentrations increase disproportionately with the dose.
What is the significance of the term "continuous intravenous infusion" in the context of steady-state drug concentrations?
A continuous intravenous infusion can achieve steady-state drug concentrations, as the rate of drug administration equals the rate of drug removal.
How does the concept of "oral medication given every 12 hours" relate to the achievement of steady-state drug concentrations?
Administering an oral medication every 12 hours can also achieve steady-state drug concentrations, as the rate of drug administration equals the rate of drug removal.
Explain the relationship between steady-state drug concentrations and the computation of new dosage regimens.
Steady-state drug concentrations are used to compute new dosage regimens, as they represent the equilibrium condition where drug levels are constant and can be used to predict the response to changes in dosing.
Learn about clinical pharmacokinetics, pharmacodynamics, and the calculation of drug loading doses based on the volume of distribution. This lecture aims to revise important concepts related to therapeutic drug monitoring.
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