Pharmacokinetics

Question 1

Bioavailability

Answer 1

Fraction of administered drug that reaches the systemic circulation unchanged. For an IV dose, F= 100%

Question 2

What exactly is the definition of volume of distribution?

Answer 2

Theoretical fluid volume required to maintainthe totalabsorbed drug amount at the plasma concentration.

Vd= Amount of drug in the body/plasma drug concentration

Question 3

Drugs that have a low volume of distribution (only go to the blood) have what characteristics?

Answer 3

Large/charged molecules; plasma protein bound

Question 4

Drugs that have a medium volume of distribution (ECF)

Answer 4

Small hydrophilic molecules

Question 5

Drugs that have a high volume of distribution (all tissues) are?

Answer 5

small lipophilic molecules, especially if bound to tissue protein

Question 6

Half life

Answer 6

Time required to change the amount of drug in the body by 1/2 during elimination

T1/2= (.7 x Vd)/ Cl

Question 7

Clearance of a drug

Answer 7

Rate of elimination/ plasma drug concentration. May be impaired with defects in cardiac, hepatic, or renal function

Question 8

Loading dose calculation

Answer 8

LD= Plasma conc x (Vd/Bioavailability)

Question 9

Maintenance dose

Answer 9

Maintenance dose= Cp x CL/F

Question 10

In renal or liver disease, maintenance dose decreases and loading dose is unchanged

Answer 10

ok

Question 11

A drug infused at steady state takes about 4-5 half lives to reach steady state under first order elimination rules

Answer 11

ok