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Medicine Term One > Drug distribution > Flashcards

Flashcards in Drug distribution Deck (33):
1

What happens once a drug has been absorbed

must be available for biological action and distribution to the tissues

2

Define drug distribution

Transfer of a Drug between the Blood and the Extra Vascular Fluids and Tissues of the body activating the drug

3

What kind of drug is biologically active

an unbound drug

4

What is Tmax and Cmax

The time to maximum plasma concentration (Tmax)
maxiumum plasma concentration (Cmax)

5

The area under the drug concentration-time curve represents

the amount of drug which reaches the systemic circulation and is available for action

6

The bioavailability of a drug is dependant on

extent of absorption and first pass metabolism

7

Drugs binding to proteins in the plasma can be affected by

Renal failure
Hypoalbuminaemia (Low plasma proteins)
Pregnancy
Other drugs
Saturability of binding

8

The less bound a drug is to plasma protein increases its ability to

cross the cell membrane and be activated

9

When is plasma protein binding matter

when binding is above 90%
because if unbound level changes above 90% there is a massive proportional increase in the amount of free drug
also important when tissue distribution is small

10

Volume Of Distribution

overall distribution of drug within the body observed in blood concentrations

11

The greater volume distribution increases the time of what

clearance

12

Define clearance

the theoretical volume of fluid from which a drug is completely removed over a period of time - basic measure of elimination

13

What is clearance dependant on

concentration
Urine flow rate
metabolism
biliary excretion for hepatic clearance.

14

What organs help clearance

Liver
Kidney
maybe gut

15

If liver and kidneys not working what is the result

accumulated drug resulting in toxicity

16

Define the half life

the time taken for the drug concentration in the blood to decline to half of the current value

17

What is half life dependant on

volume of distribution and rate of clearance

18

If half life of drug prolonged and medicine is continued this increases the volume distribution leading to

toxicity

19

What do we need to know to work out how often a drug can be administrated

half life

20

Define Drug elimination

the removal of active drug and matabolites from the body

21

What are the two parts of drug elimination

Drug metabolism
drug elimination

22

What are the primary organs for drug excretion

the kidneys

23

Where are drugs usually metabolised

Liver

24

where will all unbound drugs be filtered at

glomerulus in kidneys as long as they aren't to big

25

Factors that affect the glomerular filtration rate will reduce

the clearance of the drug

26

what is entero-hepatic circulation

Many drugs are then reabsorbed from the bile into the circulation

27

when does entero-hepatic circulation stop

when drug is metabolised in the liver or excreted by the kidneys

28

where are drugs usually conjugated - i.e. the chemical substances is terminated

the liver

29

Damage to the liver may reduce the rates of conjugation resulting in

reabsorption or an accumulation resulting in toxicity

30

What are the factors that effect drug distribution

Plasma protein binding
Blood flow - tissue mass ratio
Membrane characteristics - blood brain barrier
Transport mechanisms
Diseases and other drugs (esp renal failure, liver disease, obesity)
Elimination

31

where are some drugs selectively accumulated and what can this lead to

kidneys
eye
bone
selective toxicity

32

What is the transfer of drugs to the brain modified by and why

blood brain barrier - as is much less permeable to water-soluble drugs than is the membrane between plasma and other tissues

33

what does the duration and intensity of the pharmacological effect depend mostly on

renal function