24 Questions
What is the primary reason for dosage adjustment in patients with eliminating organ dysfunction?
To compensate for the decrease in drug ClT
What is the term for the resulting concentration of a drug when another dose is administered before the previous dose is completely removed from the body?
Drug accumulation
What is the primary factor that determines the rate of drug accumulation?
Elimination rate (half-life)
What is the purpose of a loading dose?
To achieve therapeutic concentration rapidly
What is the ratio of drug half-life to dosing interval that determines the degree of drug accumulation?
The larger the ratio, the more accumulation
How many half-lives does it take for drug accumulation to reach steady state?
5-7 half-lives
What is the term for the minimum concentration of a drug in the body?
Trough concentration
What is the formula to calculate the loading dose of a drug?
LD (mg) = Vd (L) x Desired concentration (mg/L)
What is the correct formula to calculate the elimination rate constant (k)?
$k = \frac{\ln(C1/C2)}{time}$
How is the dosing interval determined given a half-life (t1/2) of 6.3 hours for gentamycin?
12 hours
What is the desired peak concentration for gentamycin every 12 hours?
6 mg/L
Which principle states that the drug plasma concentration is constant when the administration rate equals the elimination rate?
Steady State Principle
What is the necessary condition for a steady state to be established?
Zero-order administration and first-order elimination
How is the maintenance dose calculated using the steady state principle?
$(Cl \times Css_{avg} \times \tau) \div (S \times F)$
When does the rate of drug elimination begin to increase during constant-rate IV infusion?
As the plasma concentration (Cp) increases
What is the typical time required to reach steady state, in terms of half-lives?
5-7 half-lives
What primarily determines the plasma concentration of a drug at steady state?
Rate of administration and clearance
In the context of first-order kinetics, what happens to the clearance of a drug if its concentration is halved?
Clearance remains constant
What is the relationship between total clearance (ClT) and the rate of drug elimination?
ClT is the rate of drug elimination divided by the plasma drug concentration
If two drugs have identical clearance but different volumes of distribution, which drug will have a longer half-life?
The drug with the larger volume of distribution
If a drug has a total clearance (ClT) of 4 L/hr and a volume of distribution (Vd) of 20L, what is the elimination rate constant (k)?
0.2 hr-1
How does a larger volume of distribution (Vd) affect the rate constant (k) for a given clearance (ClT)?
It decreases the rate constant (k)
What determines the peak and trough concentrations of a drug in the plasma?
Rate of drug administration and the dosing interval
Which statement accurately describes the relationship between total clearance (ClT) and the disappearance rate of the drug?
Higher ClT does not necessarily mean a faster rate of drug disappearance
This quiz covers the clinical significance of total body clearance, its impact on drug elimination rates, and its use as a monitoring parameter for organ function. It also explores dosage regimen design and adjustments for patients with organ dysfunction.
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