Pharmacology: Clinical Importance of Total Body Clearance

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What is the primary reason for dosage adjustment in patients with eliminating organ dysfunction?

To compensate for the decrease in drug ClT (correct)

To ensure a higher concentration of the drug

To prevent drug accumulation

To reach a faster rate of drug elimination

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?

Steady state

Drug accumulation (correct)

Drug elimination

Drug distribution

What is the primary factor that determines the rate of drug accumulation?

Volume of distribution (Vd)

Dosing interval

Loading dose

Elimination rate (half-life) (correct)

What is the purpose of a loading dose?

To achieve therapeutic concentration rapidly Signup and view all the answers

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 Signup and view all the answers

How many half-lives does it take for drug accumulation to reach steady state?

5-7 half-lives Signup and view all the answers

What is the term for the minimum concentration of a drug in the body?

Trough concentration Signup and view all the answers

What is the formula to calculate the loading dose of a drug?

LD (mg) = Vd (L) x Desired concentration (mg/L) Signup and view all the answers

What is the correct formula to calculate the elimination rate constant (k)?

$k = \frac{\ln(C1/C2)}{time}$ Signup and view all the answers

How is the dosing interval determined given a half-life (t1/2) of 6.3 hours for gentamycin?

12 hours Signup and view all the answers

What is the desired peak concentration for gentamycin every 12 hours?

6 mg/L Signup and view all the answers

Which principle states that the drug plasma concentration is constant when the administration rate equals the elimination rate?

Steady State Principle Signup and view all the answers

What is the necessary condition for a steady state to be established?

Zero-order administration and first-order elimination Signup and view all the answers

How is the maintenance dose calculated using the steady state principle?

$(Cl \times Css_{avg} \times \tau) \div (S \times F)$ Signup and view all the answers

When does the rate of drug elimination begin to increase during constant-rate IV infusion?

As the plasma concentration (Cp) increases Signup and view all the answers

What is the typical time required to reach steady state, in terms of half-lives?

5-7 half-lives Signup and view all the answers

What primarily determines the plasma concentration of a drug at steady state?

Rate of administration and clearance Signup and view all the answers

In the context of first-order kinetics, what happens to the clearance of a drug if its concentration is halved?

Clearance remains constant Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

How does a larger volume of distribution (Vd) affect the rate constant (k) for a given clearance (ClT)?

It decreases the rate constant (k) Signup and view all the answers

What determines the peak and trough concentrations of a drug in the plasma?

Rate of drug administration and the dosing interval Signup and view all the answers

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 Signup and view all the answers