DDS Lab Discussion: Particle Size Importance

Study Notes

Powders are intimate mixtures of finely divided drugs and chemicals, used for internal or external applications as defined by USP.
They serve various critical functions, including influencing dissolution rate, suspendability, uniform distribution, penetrability, and lack of grittiness.

Powders can act as intermediates for drugs that are usually administered as solutions or suspensions, especially for reconstitution right before administration to prevent degradation.
Common applications include antibiotic powders for syrups and powders for injection.
They are vital in the manufacturing of tablets and capsules, often blended with powdered fillers.
Powders are utilized for inhalation processes (pulmonary or nasal) and external use as dusting powders.
They can be incorporated into semisolid formulations like ointments and creams.

Trituration: Grinding drugs in a mortar to decrease particle size; effective for mixing powders as well.
Mills/Pulverizers: Employ rapidly moving blades to comminute powders, passing them through screens of specific sizes.
Levigation: Used in small-scale preparations, combining powders with minimal liquid (levigating agent) for ointments and suspensions to improve texture.

Sieving: Sorting powders based on size through a mesh.
Microscopy: Visual examination of particle sizes.
Sedimentation Rate: Evaluating the settling speed of particles in liquid.
Light Energy Diffraction: Analyzing the scattering pattern of light to determine size.
Laser Holography: Utilizing laser technology for precise measurement.
Cascade Impaction: A method for assessing particle size based on aerodynamic principles.

Spatulation: A technique for blending small powder quantities using a spatula on a flat surface, unsuitable for large volumes.
Eutectic Mixtures: Combinations of substances that change from solid to liquid at specific temperatures, known as the eutectic temperature, which varies based on the substances involved (e.g., phenol, camphor, menthol).

Eutectic Temperature: The specific temperature where the mixture transitions into a liquid phase; above it, they exist as liquids, while below, they remain solids.