drug absorption Flashcards Preview

Yr1 -S1 - Principles of Disease > drug absorption > Flashcards

Flashcards in drug absorption Deck (22):
1

there is always a correlation between plasma concentration of a drug and

the therapeutic response

2

The time to peak concentration

Tmax

3

The peak concentration

Cmax

4

The area under the drug concentration curve

AUC

5

Tmax

The more rapid the rate of absorption, the earlier the drug concentration peak

6

Cmax

Increasing the dose doesn't affect the time at which peak concentration is reached but it does increase the peak concentration

7

AUC

The area under the drug-concentration time curve represents the amount of drug which reaches the systemic circulation

8

Therapeutic range

A drug that is active over a range of concentrations

9

Below therapeutic range

no pharmacological action

10

Above therapeutic range

toxicity occurs

11

AUC

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

BIOAVAILABILITY

12

Factors effecting bioavailability

Formulation (slow release)

Ability of drug to pass physiological barriers

Gastrointestinal effects

First pass metabolism

13

Most drugs do not completely ionise in

water

14

The degree of ionisation depends on the

pH of the environment

15

Henderson-hasselbach equation

relationship between local pH and the degree of ionisation

results: small changes in pH may significantly influence the ionisation of a drug and therefore the rate of absorption or diffusion

16

Lipid solubility

ability of a drug to pass a lipid layer

17

Lipid-water partition coefficient

the ability of a drug to diffuse across a lipid barrier


ratio of the amount of drug which dissolved in the lipid and water phase when they are in contact

18

Passive Diffusion

Very common

occurs along a concentration gradient

19

Active absorption

unusual

occurs AGAINST a concentration gradient

requires carrier and energy

20

Facilitative diffusion

occurs along the concentration gradient

requires carriers

NO ENERGY needed

21

Gastrointestinal Factors

Motility (speed of gastric absorption will effect speed at which drug reaches site of absorption)

Food

Illness (malabsorption - eg celiac disease)

22

First Pass Metabolism

metabolism of drug prior to reaching systemic circulation