Drug absorption Flashcards Preview

Principles of disease JK > Drug absorption > Flashcards

Flashcards in Drug absorption Deck (38)
Loading flashcards...
1
Q

How many people are harmed by healthcare?

A

1 in 10

2
Q

Pharmaceutical

A

Get drug into the patient

3
Q

Pharmacokinetic

A

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

4
Q

Pharmacodynamic

A

Produce correct pharmacological effect - what drug does to the body

5
Q

Pharmacokinetics 4 letters

A

Absorption
Distribution
Metabolism
Excretion

6
Q

What does pharmacokinetics allow the understanding of?

A

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

7
Q

Absorption

A

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
Q

Oral

A

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

9
Q

IV

A

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

10
Q

Subcutaneous

A

For example an insulin injection

11
Q

Intramuscular

A

Vaccines in deltoid and water soluble better

Avoid 1st pass metabolism

12
Q

Other GI

A

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

13
Q

Inhalation and nasal

A

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

14
Q

Transdermal

A

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

15
Q

Plasma concentration and therapeutic response

A

Always a correlation

16
Q

Therapeutic range

A

Drug active over a range if concentrations

17
Q

What is above the therapeutic range?

A

Toxicity

18
Q

What is below the therapeutic range?

A

No or insufficient pharmacological action

19
Q

Therapeutic index

A

Range at which a drug is safe and active

20
Q

Tmax

A

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

21
Q

Cmax

A

Peak concentration ( increase dose increase c max)

22
Q

What does AUC show?

A

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

23
Q

Bioavailability

A

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

24
Q

First pass metabolism

A

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
Q

Formulation

A

Slow release preparations

26
Q

GI effect

A

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

27
Q

Pass physiological barrier

A

Particle size
Lipid solubility
pH and ionisation

28
Q

Ionisation (4 points)

A
  • 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
Q

What does the degree of dissociation depend on?

A

Environmental pH

30
Q

Ion trapping

A

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

31
Q

What do proton pump inhibitors do?

A

Reduce the amount of acid made in the stomach

32
Q

What do antacids do?

A

Neutralise the acid made by the stomach?

33
Q

Lipid solubility

A

Drug must be in solution and lipid soluble

34
Q

Lipid - water partition co efficient

A

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
Q

What does passive diffusion depend on?

A

Lipid solubility and degree of ionisation

Not saturated as no proteins used to occupy

36
Q

Active absorption

A

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

37
Q

Facilitated diffusion

A

No energy needed but carrier is so is saturable

38
Q

Filtration/bulk flow

A

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