L5 - Introduction to Dissolution and Solubility Flashcards Preview

Y2 - Normal function of GI tract > L5 - Introduction to Dissolution and Solubility > Flashcards

Flashcards in L5 - Introduction to Dissolution and Solubility Deck (11)
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1
Q

what is the rate determining step of absorbtion

A
  • rate of dissolution
2
Q

solution

A
  • mixture of two or more components that form a single, molecularly homogenous phase
3
Q

dissolution

A
  • process by which a solid dissolves in a solvent to produce a solution
  • dispersion of particles to crystal of drug to solution
4
Q

WHat are the steps in drug absorbtion

A
  • only drugs in soln can cross the intestinal wall and be absorbed int o the systemic circulation
5
Q

solubility of a substance

A
  • the amount that goes into a solution when equilibrium is established between the solute in solution and the excess (undissolved) substance
6
Q

What is the diffusion layer

A
  • high conc of compound
  • there is a diffusion gradient
  • moves toward equilibrium
  • conc is equal
7
Q

what are the meanings of the letter

A
  • dm/dt = rate of dissolution of the drug particles
  • D = diffusion coefficient
  • A = effective SA of the drug particles
  • h = thickness of the diffusion layer
  • Cs = the saturated solubility
  • C = conc in the bulk solubility
8
Q

what is the effect of stirring

A
  • reduces thickness of diffusion layer
9
Q

factors that affect dissolution rates of solids in liquids:

what is each term affected by:

A, Cs, C. D, h

A
  • A: surface area of undissolved solid
    • size of solid particles
    • total area increases as particle size reduces
    • more porous particles have a bigger surface area
  • Cs: saturated solubility of solid
    • solubility in dossolution medium
    • temperature
  • C: concentration of solute (drug) in solution
    • volume of dissolution medium
  • D; dissolution coefficient
    • dissolution medium
    • viscotity
  • h: thickness of boundary layer
    • degree of agitation, e.g. mixing
10
Q

what are the physiological factors affecting drug solution

A
  • stomach contents
    • food components
    • pH
    • buffer capacity
  • GI motility
    • transit/emptying of stomach
    • gastrointestinal secretion
    • co-administered fluids
11
Q
A
  • in fine powder form for the