Diffusion From Pill To Target Receptor

Question 1

Diffusion Def

Answer 1

Transference of a substance from an area of high chemical potential to an area of low chemical potential. Aspect of drug liberation, absorption, distribution and elimination

Question 2

Chemical Potential Def.

Answer 2

Potential energy in system due to mass diffusion. Movement of substance down concentration gradient increases system entropy (disorder)

Question 3

Lattice Theory Outline

Answer 3

Explanation of diffusion. Proposes liquids are quasicrystalline structure with pockets of empty spaces. Solutes in liquid solvents fill these empty pockets. When diffusing the solute molecules move from hole to hole with kinetic energy

Question 4

Relationship between concentration gradient and diffusion

Answer 4

The higher the concentration gradient = the faster the diffusion

Question 5

Steady State Outline

Answer 5

When equilibrated, the rate of diffusion across a barrier becomes constant with respect to time

Question 6

What aspects of development does diffusion effect

Answer 6

mixing, segregation, dissolution, filtration (purification and sterilisation) and packaging stability

Question 7

How diffusion rate is increased synthetically

Answer 7

Mechanical processing, pressure change and temp change

Question 8

Drug journey from dosage form to target receptor

Answer 8

Liberation, absorption, distribution (controlled release) and elimination

Question 9

Fick’s 1st law states

Answer 9

Diffusion rate (flux) is proportional the concentration gradient (when multiplied by negative diffusitivy)

Question 10

Flux (J) (mol/m^2/s) Def.

Answer 10

Diffusion Rate. Amount of substance flowing through unit cross section of barrier per unit time

Question 11

Conc Gradient Notation

Answer 11

dc/dx

Question 12

Diffusion Coefficent Def.

Answer 12

Diffusivity. How well given solvent can diffuse in a particular medium. Measured as rate diffusing solute transports between 2 regions with a unit conc. diff.

Question 13

Factors effecting diffusion coefficent

Answer 13

Molecular size (radius of particle), medium nature (viscosity) and system kinetic energy (temp)

Question 14

Relationship between Temperature and diffusion constant

Answer 14

Increasing Temp = increasing diffusion constant

Question 15

Relationship viscosity (resistance to shape changing) and diffusion constant

Answer 15

Increasing viscosity = decreasing diffusion coefficent

Question 16

Relationship between particle radius (a) and diffusion coefficent

Answer 16

Increasing radius = decreasing diffusivity

Question 17

Diffusion Coefficent in Aqueos Media

Answer 17

Higher d = greater diffusivity of a substance in defined medium under defined temp and pressure

Question 18

Relationship between diffusion rate and distance to target receptor

Answer 18

bigger distance = slower diffusion rate

Question 19

How patients can increase viscocity in chyme to slow drug diffusion

Answer 19

Eating before ingesting drug

Question 20

Sync-Conditions

Answer 20

There’s a 10% con. difference between 2 points. Substance moves down conc gradient consisytntly

Question 21

Non-Sync-Conditions

Answer 21

Less then 10% conc difference between 2 points. Drug builds up at 1 point (don’t flow consistently)

Question 22

Diffusion Factors

Answer 22

Temp, Conc gradient, molecular weight, drug chamical nature, solvent nature (polarity, viscosity, composition) and barrier nature (eg selectively permeable)

Question 23

Drug and Vehicle Nature Def.

Answer 23

Higher solubility of solute (drug) in solvent (mainly water) the greater the diffusivity

Question 24

What happens if equilibrium is reached across barrier

Answer 24

Diffusion and dissolution stops

Question 25

Transepithelial Ressistance

Answer 25

Electrical measure of barrier ressistance across epithelial and endothelial cellls. Different membrane barriers have different ressistance. Eg skin has high ressistance while sub-cutaneous has negligible

Question 26

Resevoir Def.

Answer 26

Pool (build up) of drug with controlling factor (polymer dam, eg plastic) at it’s interface

Question 27

Matrix Def.

Answer 27

Pool (build up) of drug with controlling factor (eg polymer gelling factor) spread evenly throughout substance

Question 28

Which pools act slower Resevoirs or Matrixes

Answer 28

Matrixes as they have to liberate every part of themselves from polymer

Question 29

Consequences of High water solubility

Answer 29

Low lipid solubility. Lower chance of membrane permeation

Question 30

Instruments Used To measure Flux

Answer 30

Ussing Chanmber, Voltohmeter and franz diffusion cell

Question 31

Elimination of Drug Outline

Answer 31

Filtration (Glomular capillaries), Reabsorption (boweman’s Capsule), secretion (pertibular capilaries0 and excretion

Question 32

Excretion Def.

Answer 32

Removal of intact water soluble drug through kidneys into urine via dialysis and osmosis