2. Process in which solid substance solubilises in a
given solvent i.e. Mass transfer from solid surface to
liquid phase.
3. Amount of solute dissolved in a given solvent under
standard condition of temperature, pH, solvent
composition and constant solid surface area.
WHY DISSOLUTION STUDY?
To study release of drug (100%)
Batch to batch drug release (uniform)
Bioavailability (equivalent)
4.
5. 1. Diffusion layer model/film theory
- Formation of stagnant film/diffusion layer
- Diffusion of soluble solute form stagnant layer to
bulk of solution.
6. 2. Danckwert’s model/Surface renewal theory
-a turbulence exists at solid-liquid interface in the
dissolution medium
-mass of eddies or packets reach the soild-liquid
interface due to eddy currents
-absorb solute by diffusion and carry it back into bulk
solution.
7. 3. Interfacial barrier model
- Reaction at solid surface is not instantaneous i.e
reaction at solid surface and its diffusion across the
interface is slower than diffusion across liquid film.
8. Quality control parameter
To test quality of tablet and capsules
Types-
I. Basket type
II. Paddle type
III. Reciprocating cylinder
IV. Flow through cell
V. Paddle over disc
VI. Rotating cylinder
VII. Reciprocating disc
9. 1. Basket type
-semi hemispherical borosilicate glass of 1000 ml
capacity
-A stainless steel basket holds a cylindrical basket
-Speed limit of basket-100rpm
-Ex- capsules, tablets, suppositories, floating dosage
form
10. 2. Paddle type
-a coated stainless steel paddle that reduces disturbance
form stirring
- It has platinum wire that protects the capsules from
floating
- Motor speed- 40rpm (tablets)
-50rpm (capsules)
-25rpm (suspension)
- Temperature- 37°C
11. 3. Reciprocating cylinder
- Used in product development for controlled release
preparation
- Used to study release of products in GI tract by exposing
them to various physiochemical conditions
- Ex- extended release formulations, chewable tablets
12. 4. Flow through cell
-2 types- open system and closed system
13. i. Open system- fresh dissolution medium pumped through
cells and then fraction received
-fraction is drawn in every 30 minutes
ii. Closed system- dissolution medium is pumped into circle
but not replaced by fresh medium
-conducted in small volumes
- ex- low dosage formulation, implants
14. 5. Paddle over disk
- It has shaft and disk assembly
- Paddle is joined with disk assembly
- Capacity-900ml
15. 6. Rotating cylinder
- It has vessel instead of basket cylinder(stainless
steel)
- Drawback- transdermal patches cannot be cut to
smaller size.
16. 7. Reciprocating Disk
- Flat bottom cylinder shaped vessel
- Capacity- 50-200ml
- Placed on disk shape holder
- Ex- controlled release formulations and small dosage
