Pharm- Kinetics/Dynamics

Question 1

What is volume of distibution?

Answer 1

Theoretical volume occupied by the total amount of drug in the body relative to its plasma conc.

V_d= amount of drug in the body/plasma drug conc.

Question 2

What is the eqn for drug clearnace (the volume of plasma cleared of drug/time)?

Answer 2

CL= rate of elimination of drug/plasma drug conc.= V_d*K_e (elimination constant)

Question 3

What is the eqn of half-life (t_1/2)?

Answer 3

The time required to change the amount of drug in the body by 1/2 during elimination (or constant infusion). Property of first-order elimination. A drug infused at a constant rate takes 4-5 half-lives to reach steady state and it takes 3/3 half-lives to reach 90% of the steady-state level

t1/2= (0.693*V_d)/ CL

Question 4

What is the eqn for loading dose?

Answer 4

C_p*V_d/ F

where C_p= target plasma conc at steady state

NOTE: In renal or liver disease, the maintainence dose usually decreases and the loading dose is usually unchanged

Question 5

What is the eqn for maintenance dose?

Answer 5

C_p*CL*tau/F

tau= dosage interval (time between doses), if not administered continuously

Question 6

Describe zero-order elimination?

Answer 6

Rate of elimination is constant regardless of Cp (i.e. constant AMOUNT of drug eliminated per unit time)

Cp decreases linearly with time

Question 7

What are some drugs with zero-order elimination?

Answer 7

Phenytoin, Ehtanol, and Aspirin

Question 8

Describe first-order elimination?

Answer 8

rate of elimination is directly proportional to the drug conc. (i.e. constant FRACTION of drug eliminated per unti time). Flow-dependent elimination

Cp decreases expontentially with time

study pg. 244

Question 9

Note about urine pH and urine elimination

Answer 9

Ionized spp. are trapped in urine and cleared quickly while neutral forms can be reabsorbed

Question 10

Difference between -ximab and -zumab endings

Answer 10

• ximab= chimeric monoclonal Ab
• zumba- humanized monoclonal Ab