Pharmacokinetics

Question 1

Pharmacokinetics

Answer 1

The study of what the drug does to the body

Question 2

ADME

Answer 2

Absorption
- Inhaled (<100%)
- Oral (<100%)
- Intravenous (100% bioavailability)

Distribution (influenced by)
- Lipid vs. water solubility
- Plasma protein binding
- Tissue binding
- Circulation to tissues

Metabolism and Excretion
- Clearance in liver and kidneys
- CLtotal = CLrenal + CLhepatic
- Volume of plasma from which drug is removed per unit time
- CL = dose/AUC or CL = (0.693*V)/t1/2

Question 3

Bioavailability

Answer 3

Fraction of unchanged drug reaching systemic circulation after administration

Question 4

Cmax and Cmin

Answer 4

Cmax - Maximum plasma concentration
Cmin - Minimum plasma concentration

Question 5

Plasma concentration-time profile

Answer 5

Plasma concentration (y, μg/ml) vs. Time post dose (x, hour)

Question 6

First order elimination

Answer 6

Constant proportion of drug is eliminated per unit time
k = elimination rate constant, fraction of drug eliminated per unit time

Equation of line • C = Coxexp(-kt)

Question 7

Half life

Answer 7

Time taken for drug concentration to decline by one half

t1/2 = 0.693/k (first order)

Majority (~97%) of drug will be eliminated after 5 half lives, steady state then reached

Dependent on volume of distribution (V, L or mL) and clearance (CL, L/h or mL/min) Hello

Question 8

Body fluids (70kg adult)

Answer 8

Extracellular water - 15L
Intracellular water - 25 L
Plasma - 3L
Blood - 5L