Dispersed Systems

Dispersed system:  It is liquid preparations containing undissolved or immiscible drug distributed throughout a vehicle.  The substance distributed is referred to as the dispersed phase.  The vehicle is termed the dispersing phase or dispersion medium. Together, they produce a dispersed system.

 The particles of the dispersed phase could be: 1- Solid (suspension) 2- Liquid (emulsion) 3- Gas (aerosol)

 The particles of the dispersed phase vary widely in size, from large particles visible to the naked eye down to particles of colloidal dimension, falling between 1.0 nm and 0.5 μm.

Classification of dispersed system:  Coarse dispersions (10-50 µm) (suspensions and emulsions).  Fine dispersions ( µm) (Magmas and gels).  Colloidal dispersions (1.0 nm-0.5 μm).

Solutions  solutions may be prepared from any combination of solid, liquid, and gas.  In pharmacy, however, interest in solutions is for the most part limited to preparations of a solid, a liquid, and less frequently a gas solute in a liquid solvent.  In pharmaceutical terms, solutions are “liquid preparations that contain one or more chemical substances dissolved in a suitable solvent or mixture of mutually miscible solvents”

Classification  According to pharmaceutical use, solutions may be classified as 1- Oral. 2- Otic. 3- Ophthalmic 4- Topical.

 According to their composition or use, solutions may be classified as other dosage forms. For example:  Syrups.  Elixirs.  Spirits.  Aromatic waters.  Tinctures or fluidextracts.  Injections.

 Oral solutions, syrups, elixirs, spirits, and tinctures are prepared and used for the specific effects of the medicinal agents they carry.  Solutes other than the medicinal agent are usually present in orally administered solutions. These additional agents are frequently included to provide color, flavor, sweetness, or stability.

 For single-solute solutions and especially for multiple-solute solutions, the pharmacist must be aware of the solubility characteristics of the solutes and the features of the common pharmaceutical solvents.  Each chemical agent has its own solubility in a given solvent. For many medicinal agents, their solubilities in the usual solvents are stated in the United States Pharmacopeia–National Formulary (USP– NF) as well as in other reference books.

To be continued ….