THEORIES OF DISPERSION AND PHARMACEUTICAL DISPERSION (EMULSIONS AND SUSPENSIONS, SMEDDS) PREPARATION AND STABILITY PDF | PPT
Description: This document provides comprehensive insights into the theories of dispersion and pharmaceutical dispersion systems, including emulsions, suspensions, and self-microemulsifying drug delivery systems (SMEDDS). It covers preparation methods, stability factors, interfacial phenomena, and applications.
Keywords: Dispersion Systems, Emulsions, Suspensions, SMEDDS, Stability, Interfacial Phenomenon, Wetting Agents, Micellar Solubilization, PDF Download, PPT Notes
THEORIES OF DISPERSION AND PHARMACEUTICAL DISPERSION (EMULSIONS AND SUSPENSIONS, SMEDDS) PREPARATION AND STABILITY
Dispersion systems are integral to pharmaceutical formulations, as they enhance the solubility, bioavailability, and stability of drugs. These systems include emulsions, suspensions, and advanced formulations like self-microemulsifying drug delivery systems (SMEDDS). Below is a detailed exploration of the topic:
Introduction and Classification
Dispersion systems involve the distribution of one phase (dispersed phase) within another (continuous phase). They are classified based on particle size:
- Coarse Dispersions: Include suspensions and emulsions with particle sizes >100 nm.
- Colloidal Dispersions: Particle sizes range from 1–100 nm.
- Molecular Dispersions: True solutions with dissolved molecules.
Interfacial Phenomenon
The interface between phases plays a crucial role in the stability of dispersions. Key concepts include:
- Surface Tension: The cohesive force at the liquid-air interface.
- Interfacial Tension: The force between two immiscible liquids.
- Wetting Phenomenon: The ability of a liquid to spread over a solid surface.
Adsorption and Surface Active Agents
Adsorption occurs when molecules accumulate at interfaces, reducing interfacial tension. Surface-active agents (surfactants) stabilize dispersions by forming a protective layer around dispersed particles. Examples include:
- Anionic surfactants (e.g., sodium lauryl sulfate).
- Cationic surfactants (e.g., benzalkonium chloride).
- Non-ionic surfactants (e.g., polysorbates).
Micellar Solubilization
Micelles are aggregates of surfactant molecules that solubilize hydrophobic drugs in their hydrophobic core. This phenomenon enhances drug bioavailability and is widely used in pharmaceutical formulations.
Solubilization in Pharmacy
Solubilization techniques improve the dissolution of poorly soluble drugs. Methods include:
- Use of co-solvents.
- Formation of micelles or liposomes.
- Self-microemulsifying drug delivery systems (SMEDDS).
Emulsions
Emulsions are thermodynamically unstable systems consisting of two immiscible liquids stabilized by an emulsifying agent.
- Types: Oil-in-water (O/W) and water-in-oil (W/O).
- Stability Factors: Viscosity, particle size, and zeta potential.
- Applications: Oral, topical, and parenteral formulations.
Colloids
Colloids are intermediate-sized particles dispersed in a continuous phase. Types include:
- Hydrophilic Colloids: Stabilized by hydration (e.g., gelatin).
- Hydrophobic Colloids: Require stabilizers (e.g., silver halides).
Suspensions
Suspensions are coarse dispersions where solid particles are suspended in a liquid medium.
- Desirable Qualities: Uniformity, ease of redispersion, and stability.
- Settling: Governed by Stokes' law; minimized by flocculating agents.
- Flocculation: Aggregation of particles to prevent caking.
Self-Microemulsifying Drug Delivery Systems (SMEDDS)
SMEDDS are isotropic mixtures of oil, surfactant, and co-surfactant that spontaneously form microemulsions upon dilution. They enhance the bioavailability of poorly soluble drugs.
Applications
Dispersion systems are used in various pharmaceutical applications, including:
- Oral formulations for improved bioavailability.
- Topical formulations for controlled release.
- Parenteral formulations for targeted delivery.
References
For further reading, refer to:
- Textbooks on pharmaceutical technology and formulation science.
- Research articles on emulsions, suspensions, and SMEDDS.
- Regulatory guidelines for stability testing and formulation development.
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