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Flashcards in Pharmacokinetics - ADME Deck (55)
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1

What is the pharmacokinetic process?

Getting the drug to the site of action

2

What is the pharmacodynamic process?

Producing the correct pharmacological effect

3

What four events happen as part of the pharmacokinetic process?

Absorption
Distribution
Metabolism
Excretion

4

What is drug absorption?

movement of the unchanged drug from site of administration to systemic circulation

5

What is Tmax?

time taken for a drug to reach peak concentration in the body

comes earlier if absorption if the drug is more rapid

6

What is Cmax?

peak concentration of the drug in the body

affected by increases in dosage

7

What is AUC?

the amount of the drug that reaches the systemic circulation

8

What is bioavailability?

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

9

What is the therapeutic range of a drug?

the area where drug concentration if safe and active

above = toxicity
below = ineffective

10

What are the factors that effect the bioavailability of oral absorption if drugs?

- formulation
- physiological barriers
- gastrointestinal effects
- first pass metabolism

11

What type of drugs are absorbed through diffusion?

Non-ionised drugs (weak acids/bases, changes in pH change ability to diffuse)

Lipophilic drugs (must be lipid-soluble to diffuse through lipid membranes)

12

What must drugs resemble in order to be absorbed by active transport?

Naturally-occurring compounds

13

What is the main gastrointestinal factor that influences drug absorption?

Motility;
- speed of gastric absorption
- affected by food/drink/illnesses

14

What illnesses can affect GI motility?

- Coeliac disease (gives rise to malabsorption)
- Migraine (reduces the rate of stomach emptying)

15

What is the first pass metabolism?

the metabolism of a drug before it can reach the systemic circulation

i.e. a drug could be fully metabolised before reaching the blood, e.g. insulin (reason for IV administration)

16

Why are other routes of drug absorption used?

- absorption rate can be changed with different formulation
- drugs with small volumes
- blood flow differences
- avoiding the first pass metabolism

17

Name four sites of drug administration, other than oral

Sublingual/Buccal
Rectal
Nasal
Transdermal

18

What is drug distribution?

the reversible transfer of a drug between blood and extravascular fluids/tissues in order for it to become active

19

What factors can influence drug distribution?

Plasma protein binding
Tissue perfusion
Membrane characteristics
Transport mechanisms
Diseases
Other drugs
Elimination

20

What is plasma protein binding?

when drugs bind to plasma proteins such as albumin, nullifying their effects

21

What can affect the amount of a drug that is bound to plasma proteins?

- renal failure
- hypoalbuminaemia
- pregnancy
- other drugs (by displacement)

22

Name three parameters of the therapeutic range

Apparent volume of distribution (Vd)

Clearance (Cl)

Half-life (T1/2)

23

What is apparent volume of distribution?

theoretical volume needed to contain the total amount of a drug in the blood plasma if the drug was present in the same concentration throughout the body (L/Kg)

24

What is caused by a greater Vd?

greater ability of a drug to diffuse to/through membranes

25

What is clearance?

volume of fluid from which a drug is completely removed over a period of time (ml/min)

26

What does renal clearance depend on?

- concentration

- urine flow rate

27

What does hepatic clearance depend on?

- metabolism

- biliary excretion

28

What is the half-life of a drug?

time taken for the drug concentration to decline by half its current value

29

What does T1/2 depend on?

- clearance

- apparent volume of distribution

30

What is drug elimination?

removal of active drug/metabolites