Powders and Granules Flashcards
What are the two things that powders may describe?
- PHYSICAL FORM of a material- a dry substance composed of finely divided particles
- Type of PHARMACEUTICAL PREPARATION- a medicated powder intended for internal or external use.
What does particle size impact?
- * PLUS-D**
- Penetrability of particles for inhalation
- Lack of grittiness for dermatological s
- Uniformity of dose
- Suspendability of suspensions (stokes law)
- Dissolution Rate
Importance of particle size:
MIXING, MIGRATION, COLOR, DERMATOLOGICALS
- Uniform particle size aids in mixing and distribution
- Migration may occur with differences in particle size
- Differences may change the color intensity of a powder
- Especially important in dermatologicals
A decrease in particle size…
Increases surface area
Increases bio availability
The study of small particles:
MICROMERITICS
- P article size & particle size distribution
- U niformity
- M orphology
- P orosity
- V olume
- C ompatibility with other formulation components
- F low
What is the purpose of particle size analysis?
To obtain quantitative data on the size, distribution and morphology of powders.
What are the sizes of pharmaceutical powders?
May range in size from extremely course (about 10mm) to extremely fine (about 1 micron or less)
USP terms for particle size
Very course, coarse, moderately course, fine, very fine.
Smaller sieve # = Larger particle size
What is a sieve?
Helps to determine particle size as well as get particle size where it needs to be.
What are the 5 methods of Particle Size Analysis?
- Sieve Analysis
- Microscopy
- Sedimentation Rate
- Laser light scattering or diffraction
- Cascade impaction
- Particles are passed by mechanical shaking though a series of sieves of known and successively smaller size.
- The proportion of powder passing through or being withheld on each sieve is determined
Sieve Analysis
Particle size is determined by a visual observation with the use of a calibrated grid background or other measuring device.
Microscopy
Simulate inhalation, inhalation devices, to determine analyze particle size
Andersen Cascade Impactor
What is powder flow IMPACTED by?
- SIZE
- SHAPE
- POROSITY
What is powder flow CHARACTERIZED by?
- Angle of response
* Carr/Hausner Index (Compressibility Index)
- Estimates flow properties
- Measure the angle formed when powder is allowed to flow freely from a known height
- Tan O = h/r
Angle of Response
Powders with low angles of response flow freely
- Method to determine powder flow and compressibility
- Useful in determining storage needs
- Weigh known volume of powder and mechanically drop from a given height and determine volume
Tapped and Bulk Density
A smaller compressibility index means…
Better flow
A larger compressibility index means
Less flow
The process of reducing a particle size of a solid substance to a finer state of subdivision
Comminution
What are the objectives of particle size reduction
- Facilitate crude drug extraction
- Increase the dissolution rates of drugs
- Aid in the formulation process
- Enhance absorption
Trituation, Pulverization, and Levigation are forms of what type of Particle size reduction
EXTEMPORANEOUS Particle size reduction
Continued rubbing of a solid in a mortar with a pestle to reduce particle size
Trituration
Comminution by utilizing a solvent that can be easily removed.
Pulverization