Clinical Applications of Pharmacokinetics Cont.

Question 1

Multi-Dose Treatment Regimens

Answer 1

Many drugs are administered repeatedly over an extended period of time, with the goal to achieve and maintain an effective drug level without causing harm to the animal “Goldilocks or Just Right” Zone - balance b/t adverse/toxic effects and lack of therapeutic efficacy

Question 2

Half life of a drug is dependent upon which two things?

Answer 2

Clearance and volume of distribution T1/2 = 0.693*Vd/Clb Half-life is useful to estimate time that a drug will stay in a therapeutic range

Question 3

Factors affecting Vd

Answer 3

Aging = possible decrease Obesity = greater distribution into adipose Ascites = greater distribution into fluid

Question 4

One-compartment model

Answer 4

Describes distribution and elimination after an IV bolus dose; entire body viewed as one single compartment -follows first order kinetics

Question 5

Two compartment model

Answer 5

Includes a peripheral compartment that drugs may distribute to

Central = blood and well-perfused organs

Peripheral = poorly perfused tissues

Question 6

Steady state

Answer 6

Describes the plasma drug concentration that is reached when the rate of drug entry into the body and the rate of drug elimination equal one another

Question 7

The time it takes a drug to achieve steady state concentrations in the plasma is solely dependent on _________________

Answer 7

The half-life of the drug

Question 8

How many half lives of sustained drug administration does it take for a drug to achieve a steady state?

Answer 8

5

Question 9

At what point is the next dose in a multi-dose treatment given?

Answer 9

When the previous dose has reached its half life

Question 10

How can you achieve steady state more rapidly?

Answer 10

• Provide a loading dose (Vd * Cpss)
• Shorten the dosage interval (small fluctuations)
• Slow absorption (e.g. PO)
• Renal insufficiency

Question 11

Therapeutic drug monitoring

Answer 11

Drug concentrations are measured in the patient, using pharmacokinetics to analyze blood plasma concentrations and make drug dosage adjustments

Question 12

When do you use therapeutic drug monitoring?

Answer 12

• drugs with narrow therapeutic ranges
• expected or desired effect of drug is not observed
• patient has physiological condition that affects therapeutic activity of the drug (i.e. renal insufficiency)