Drug absorption

Question 1

How many people are harmed by healthcare?

Answer 1

1 in 10

Question 2

Pharmaceutical

Answer 2

Get drug into the patient

Question 3

Pharmacokinetic

Answer 3

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

Question 4

Pharmacodynamic

Answer 4

Produce correct pharmacological effect - what drug does to the body

Question 5

Pharmacokinetics 4 letters

Answer 5

Absorption
Distribution
Metabolism
Excretion

Question 6

What does pharmacokinetics allow the understanding of?

Answer 6

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

Question 7

Absorption

Answer 7

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

Question 8

Oral

Answer 8

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

Question 9

IV

Answer 9

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

Question 10

Subcutaneous

Answer 10

For example an insulin injection

Question 11

Intramuscular

Answer 11

Vaccines in deltoid and water soluble better

Avoid 1st pass metabolism

Question 12

Other GI

Answer 12

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

Question 13

Inhalation and nasal

Answer 13

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

Question 14

Transdermal

Answer 14

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

Question 15

Plasma concentration and therapeutic response

Answer 15

Always a correlation

Question 16

Therapeutic range

Answer 16

Drug active over a range if concentrations

Question 17

What is above the therapeutic range?

Answer 17

Toxicity

Question 18

What is below the therapeutic range?

Answer 18

No or insufficient pharmacological action

Question 19

Therapeutic index

Answer 19

Range at which a drug is safe and active

Question 20

Tmax

Answer 20

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

Question 21

Cmax

Answer 21

Peak concentration ( increase dose increase c max)

Question 22

What does AUC show?

Answer 22

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

Question 23

Bioavailability

Answer 23

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

Question 24

First pass metabolism

Answer 24

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

Question 25

Formulation

Answer 25

Slow release preparations

Question 26

GI effect

Answer 26

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

Question 27

Pass physiological barrier

Answer 27

Particle size Lipid solubility pH and ionisation

Question 28

Ionisation (4 points)

Answer 28

- 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

Question 29

What does the degree of dissociation depend on?

Answer 29

Environmental pH

Question 30

Ion trapping

Answer 30

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

Question 31

What do proton pump inhibitors do?

Answer 31

Reduce the amount of acid made in the stomach

Question 32

What do antacids do?

Answer 32

Neutralise the acid made by the stomach?

Question 33

Lipid solubility

Answer 33

Drug must be in solution and lipid soluble

Question 34

Lipid - water partition co efficient

Answer 34

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

Question 35

What does passive diffusion depend on?

Answer 35

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

Question 36

Active absorption

Answer 36

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

Question 37

Facilitated diffusion

Answer 37

No energy needed but carrier is so is saturable

Question 38

Filtration/bulk flow

Answer 38

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