Ch.7: Principles of Pharmacokinetics

Question 1

AMDUCA*

Answer 1

Animal Medicinal Drug Use Clarification Act. Provided legal basis for ELDU by vets

Question 2

key PK properties for a drug (4)*

Answer 2

• bioavailability (F)
• volume of distribution (Vd)
• clearance (Q)
• elimination half-life (t1/2)
• *can be changed by disease processes or other conditions (aging)**

Question 3

bioavailability*

Answer 3

the fraction of the drug that is absorbed and gets into the bloodstream relative to the amt. that would get into the bloodstream if you gave it by direct IV injection (a fractional measure)

Question 4

In the formula Vd = total body drug dose/plasma conc. Plasma conc. refers to what?*

Answer 4

the expected highest plasma conc. that will be achieved with the drug

Question 5

T/F: IV doses remain primarily in the bloodstream with drugs that have a low Vd. What are the causes of this?*

Answer 5

T. causes include poor permeability, high water solubility, high protein binding, limited diffusion in tissues

Question 6

Name 1 drug with high Vd*

Answer 6

Propanolol

Question 7

Name 1 drug with low Vd*

Answer 7

Theophylline

Question 8

Chars. of zero order kinetics*

Answer 8

• drug eliminated at constant rate
• rate of drug elim. is unrelated to drug conc.
• potentially dangerous
• rare for the drugs we use

Question 9

Chars. of first order kinetics*

Answer 9

• drug elim. at exponential rate
• fixed fraction of drug eliminated per unit time
• rate of drug elim. is proportional to drug conc.
• safer
• can convert to zero order kinetics if elim. process becomes saturated

Question 10

Reasons for prolonged drug treatment*

Answer 10

1) drug therapy controls symptoms, but doesn’t cure the underlying dz
2) drug cures the dz, but therapeutic success requires prolonged exposure to drug

Question 11

The time required to achieve steady-state drug conc. in plasma depends solely on the ___ of the drug*

Answer 11

half-life

Question 12

when are loading doses used?*

Answer 12

a larger dose of drug given for initial dose to bump up the plasma conc. so it doesn’t take so long to reach a steady state

Question 13

Steady-state levels of peak and trough drug conc. are determined by:**

Answer 13

drug dose and dosing frequency (interval)

Question 14

Factors that alter steady state*

Answer 14

• slow absorption
• PO admin.
• irregular doses
• missed doses

Question 15

2 approaches used to alter dosing regimen when drug is primarily cleared by the kidney*

Answer 15

• interval extension

- dose reduction

Question 16

2 common methods for altering dose regimens*

Answer 16

1) individualized regimen (based on actual drug levels in the patient)
2) creatinine clearance (compared to normal urinary levels)