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Principles of disease JK > Drug absorption > Flashcards

Flashcards in Drug absorption Deck (38):
1

How many people are harmed by healthcare?

1 in 10

2

Pharmaceutical

Get drug into the patient

3

Pharmacokinetic

Get drug to site of action - what body does to the drug

4

Pharmacodynamic

Produce correct pharmacological effect - what drug does to the body

5

Pharmacokinetics 4 letters

Absorption
Distribution
Metabolism
Excretion

6

What does pharmacokinetics allow the understanding of?

Dosage, drug handling, harm potential, drug administration and patient variability

7

Absorption

Blood must enter the bloodstream and be distributed to site of action to have biological action
The process of movement of unchanged drug from site of administration to systemic circulation

8

Oral

Always consider purpose and site of drug, effects, speed, reliability etc

9

IV

Small volume and depends on blood flow to site, right into blood

10

Subcutaneous

For example an insulin injection

11

Intramuscular

Vaccines in deltoid and water soluble better
Avoid 1st pass metabolism

12

Other GI

Rectal, sublingual - under tongue to avoid 1st pass metabolism

13

Inhalation and nasal

Better for volatile agents
Metabolism in lungs
5-10% absorbed

14

Transdermal

Avoids first pass metabolism but few substances well absorbed eg nicotine patches

15

Plasma concentration and therapeutic response

Always a correlation

16

Therapeutic range

Drug active over a range if concentrations

17

What is above the therapeutic range?

Toxicity

18

What is below the therapeutic range?

No or insufficient pharmacological action

19

Therapeutic index

Range at which a drug is safe and active

20

Tmax

Time to peak concentration ( rapid rate of absorption decreases this)

21

Cmax

Peak concentration ( increase dose increase c max)

22

What does AUC show?

Area under the curve equivalates to the amount of drug reaching the systemic circulation

23

Bioavailability

Amount of drug in system/circulation which is ready for action
IV = 100%

24

First pass metabolism

Metabolism of any drug prior to reaching systemic circulation and is a limit for the oral route
Metabolism by acid/enzyme in lumen gut wall and liver

25

Formulation

Slow release preparations

26

GI effect

Food
Illness - malabsorption and diarrhoea eg coeliac disease, migraine reduce stomach emptying
Gut motility - gastric absorption

27

Pass physiological barrier

Particle size
Lipid solubility
pH and ionisation

28

Ionisation (4 points)

- Most drugs do not completely ionise in water
- Most drugs are weak acids or bases
- Ionised drugs DO NOT cross the membrane
- Unionised distribute until equilibrium

29

What does the degree of dissociation depend on?

Environmental pH

30

Ion trapping

Acidic drug will be more concentrated in the compartment with high pH

31

What do proton pump inhibitors do?

Reduce the amount of acid made in the stomach

32

What do antacids do?

Neutralise the acid made by the stomach?

33

Lipid solubility

Drug must be in solution and lipid soluble

34

Lipid - water partition co efficient

Ability of drug to diffuse across lipid barrier
Ratio of amount of drug dissolve lipid: water phase
Lipid soluble reach brain, testes, liver, ovaries
Not lipid soluble not absorbed eg gentamicin

35

What does passive diffusion depend on?

Lipid solubility and degree of ionisation
Not saturated as no proteins used to occupy

36

Active absorption

Specific, unusual, saturable and requires a carrier +energy
Eg iron upake by brain
Drugs must resemble naturally occurring compound

37

Facilitated diffusion

No energy needed but carrier is so is saturable

38

Filtration/bulk flow

Channels in membrane - low molecular size
Pressure differences across membrane drives it
Usually water soluble drugs eg ammonia, water
Real excretion, remove drug from CSF and enter the liver