Drug Half Life and Dosing

Question 1

Volume of distribution

Answer 1

Volume necessary to account for the total amount of drug in the body if it were present throughout the body at the same concentration found in the plasma

Question 2

Equation for volume of distribution

Answer 2

Vd = dose / plasma concentration

Question 3

Half life (t1/2)

Answer 3

Time required to change the amount of drug in the body by one-half during elimination

Question 4

Equation for half life

Answer 4

t1/2 = (0.7 x Vd) / CL

Question 5

Plateau principle

Answer 5

Time to reach steady state is dependent only on elimination half life and is independent of dose size and frequency of administration

Question 6

Maintenance dose

Answer 6

Maintains steady state, just enough drug is given in each new dose to replace the amount lost from the previous dose

Question 7

Loading dose

Answer 7

Used when time to reach steady state is prolonged- drugs with long half lives, large Vd

Question 8

Equation for loading dose

Answer 8

Loading dose = Vd x TC

Question 9

Equation for maintenance dosing rate infusion

Answer 9

Dosing rate = Cl x TC

Question 10

Equation for maintenance dosing rate for intermittent doses

Answer 10

Maintenance dose = (dosing rate / F) x dosing interval