Lecture 10 Flashcards
Powders & Granules
Powders
Mixture of drug, finely divided drugs, and/or chemicals that may be intended for internal or extended use
Granules
Agglomerates of powders materials, that may be used per se for the medicinal value of the content, or used for making other pharmaceutical dosage forms for tablets or capsules.
Micromeritics
Science and technology of small particles
Derived Properties of Powders/Granules (5)
- Porosity of powder
- Packing arrangement
- Density
- Flow (angle of repose)
- Dissolution rate
Fundamental Properties of Powders/Granules (4)
- Particle size
- Size distribution
- Shape (morphology)
- Surface Area
Influencers of Size Influences (5)
- Dissolution rate of particles (decreased size and increased rate)
- Suspendability of particles (suspension)
- Uniform distribution of a drug in a powder mixture (dose-to-dose uniformity)
- Inhaled drug delivery
- Lack of grittiness of particles in dermal ointments, creams, and ophthalmic preparations
Size + Solubility
Smaller the size, greater the surface area, the higher the solubility.
Determinants of Particle Size (5)
- Sieving
- Microscopy
- Sedimentation
- Light diffraction/scattering
- Cascade impaction
Sieving Method
- particle size analysis
- from a cm down to a few nm
- Passing powders through standard sieves while being shaken
- Ranges from very coarse, moderately coarse, coarse, fine, and very fine
- Higher the sieve number the finer the powder
Mesh Size Meaning
Number of sieves per inch. Smaller the opening as the mesh size number increases
Particle Size Distribution Importance
Formulations have same average particle size but different size distributions
Powder Shape
- Aka Morphology
- Shape affects surface area of particle and behavior when surrounded by other particles
- Behaviors affected are flow and packing
Shape Characterizations (5)
- Spherical
- Rounded
- Acicular (needle-like)
- Flake
- Irregular
* *Determined via microscopic techniques**
Components Affecting Surface Area (2)
- Size reduction (micronized)
2. Shape - can increase or decrease SA depending on shape
Porosity
Measures of void spaces in bulk powder
- Low porosity - little void volumes in powder
- High porosity - large void volumes in powder (more reaction potential)
Porosity Affect (3)
- Disintegration/dissolution
- Drug diffusion
- Absorption
Two Ways Drugs can Enter System
- Diffuse from the matrix
2. Matrix dissolves to release the drugs (dissolution)
Ideal Packing Assumptions
Uniformed Size, sperical powder beds
Ideal Packing Arrangements (2)
- Closest or rhombohedral - ~26% porosity
2. Open or cubic - ~48% porosity
Non-Ideal Packing Scenarios (3)
- Neither spherical nor uniform size - intermediate packing
- Large particle size distribution - smaller particle shift between layers, lower porosity
- Form aggregates - bridging, arching, clinging, and ratholing in packing. Higher porosity
Density
Ratio of mass of sample to volume
Density Depends on (2)
- Type and arrangement of atoms in molecule
2. Arrangement of molecules in sample (crystalline)
Density Influences (3)
- Flow
- Powder blending
- Tableting/capsuling
Types of Density (2)
- Bulk Density
2. Tap Density
Flow Properties and Affects
Either free flowing or stick
Affects:
- Blending - homogeneity of mixture
- Tablet/capsuling - content and weight uniformity
Factors Influencing Powder Flow (6)
- Particle morphology
- Crystallinity
- Particle density
- Surface area
- Particle size and size distribution
- Moisture in powder
Angle of Repose
- Pouring of powder into a pile
- Angle created from the edge of pile to the surface is the angle of repose
- The smaller the angle of repose the better the powder flow
Comminution
Micronization of Drugs
Comminution Types (3)
- Small scale - mortar & pestle to titrate or comminution
- Large scale - mills and pulverizers
- Levigation - small scale prep of ointment or suspension. Grind down powders and add in small amount of liquid or base to further grind it down before adding in remaining base. Reduces grittiness of powders.
