Drug Distribution

Question 1

Unbound drug - biologically active or inactive?

Answer 1

active

to be active - drug leave blood enter inter/intracellular space

Question 2

Amount of bound drug can be changed by:

Answer 2

Renal failure
Hypoalbuminaemia
Pregnancy
Other drugs
Saturability of binding

Question 3

Theoretical vol of fluid - from which drug is completely removed over a period of time

(vol of blood cleared of drug)

Answer 3

clearance (ml/min)

Question 4

half life (t1/2)

Answer 4

the time taken for the blood drug conc to decline to half conc
e.g. 4hrs taken for 10mg/l drug to 5mg/l = half-life is 4 hrs

Question 5

primary organ of elimination

Answer 5

kidney

Question 6

primary organ of metabolism

Answer 6

liver

Question 7

Kc (equilibrium constant) is dependant on

Answer 7

ph of compartment
binding capacity
barriers permeability

Question 8

how much drug needs to be within body to get certain [plasma]

total amt of drug in body/conc of drug in plasma

Answer 8

volume of distribution (Vd)

increased Vd = increased diffusion across memb

Question 9

tissue distribution affected by

Answer 9

disease and other drugs
transport mech
memb characteristics
tisc perfusion
plasma pr- binding
elimination

plasma pr- binding - reversible
1. binding sequesters drug - increase that compartments storage capacity, once equilibrium reached (unbound=bound) unbound moves to another compartment to equal adjacent compartments

2. Unbound drug sequestered again by pr- in that compartment - continues to equilibriate all compartment

3.

Question 10

T1/2 depends on:

Answer 10

0.693Vd/Cl

Volume of distribution and Clearance
Increased T1/2 = Increased Vd = Increased Drug Toxicity = Decreased Clearance

Low Vd = 3L - stay in circ
Increased Vd = increased drug in lipid tisc e.g. brain, liver

Question 11

Loading Dose - how many half life needed to stabilise plasma [drug]?

Answer 11

4/5 Half life

Summary of product characteristics (SMPC) = gives info on half life