Lecture 8 - PRINCIPLES OF PHARMACOTHERAPEUTICS

Question 1

What happens to the plasma concentration during repeated administration?

Answer 1

If a drug that is eliminated by first-order kinetics, is administered repeatedly, the average plasma concentration of the drug will increase until a mean steady-state level is reached.

Question 2

When is the different levels of steady state achived?

Answer 2

• Levels will be at the high point of the steady state range shortly after a dose is administered.
• Levels will be at the low point immediately before administration of the next dose.

Question 3

How is the mean of plasma concentration during steady state?

Answer 3

The mean of plasma concentration during steady-state (Cpss) is 1.44 times higher then the Cmax after the first application.

Question 4

When is a large loading dose needed?

Answer 4

-A large loading dose may be needed initially when the therapeutic concentration of a drug in the plasma must be achieved rapidly.

Question 5

What is the :Maintenance dose rate?

Answer 5

-Maintenance dose rate is the dose of a drug required per unit time to maintain the wanted steady-state level in the plasma to sustain a specific therapeutic effect.

Question 6

How can the magnitude of fluctuations (shifts/changes) at the steady state can be controlled?

Answer 6

• The magnitude of fluctuations can be controlled by the dosing interval.
• A shorter dosing interval decreases fluctuations, and a longer dosing interval increases them.

Question 7

What can may hurt the steady-state level?

Answer 7

Too long intervals between application of doses may hurt the steady-state level.

Question 8

How do you calculate the loading dose?

Answer 8

• To calculate the loading dose, select the desired plasma concentration of drug and multiply by the Vd.
• After administration of the loading dose , one administers the drug at the maintenance dose rate to maintain the drug concentration at the desired steady-state level.

Question 9

To remain at steady state, the dose rate must equal the ….

Answer 9

To remain at steady state, the dose rate must equal the elimination rate; that is, the rate at which the drug is added to the body must equal the rate at which it is eliminated.

elimination rate = Cl × Drugplasma.