Therapeutic Drug Monitoring

Question 1

ED50

Answer 1

What is drug dose where you have 50% chance of effectiveness?

Question 2

TD50

Answer 2

what does would you expect 50% chance of toxicity

Question 3

TI (therapeutic index)

Answer 3

TD50 / ED50

the higher the ratio, the safer the drug

Question 4

Therapeutic Range

Answer 4

Minimum toxic dose - Minimum Effect dose

Question 5

CYP2C19

Answer 5

Effects Warfarin metabolism

Question 6

VKOR

Answer 6

Vitamin K epoxide reductase

effects warfarin target

Question 7

Pharmacokinetics

Answer 7

what the patient does to the drug

absorption, distribution, binding, elimination

all about blood levels

Question 8

Pharmacodynamics

Answer 8

what the drug does to the patient

the study of uptake, movement, binding, and interactions of the pharmacologically active molecules at their tissue site(s) of action.

Question 9

Bioavailability

Answer 9

the proportion of the administered dose which is absurd into the blood stream

IV (best) vs Oral

Question 10

Distribution phase

Answer 10

time required for drug to equilibrate with the tissues

usually minutes

Question 11

Volume of Distribution

Answer 11

the drug’s propensity to either remain in the plasma or redistribute to other tissue compartments

Vd: proportionality constant that relates total mount of drug in the body to the drug concentration at a given time

Vd = Dose / c (current concentration) - c0 (initial concentration)

highly fat soluble drugs Vd is very large

Question 12

Clearance

Answer 12

• rate at which drug is removed from the blood stream
• zero order - constant amount per time independent of concentration
  
  • ethanol, phenytoin are examples
• first order - constant proportion removed over time
  
  • most drugs

Question 13

Steady State

Answer 13

time at which the drug concentration is stable upon repeated measurements

about 5 half-lifes