L5 - Introduction to Dissolution and Solubility Flashcards
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
