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Aqueous solutions contain one or more drugs dissolved in water. There are 2 categories: solutions for oral use and solutions for injection which are sterile liquids or suspensions packed in suitable containers. The most common aqueous vehicles for injection preparation are water for injection and sodium chloride injection. Injections are available in sealed glass ampoules or vials.
Aqueous suspensions consist of one or more chemicals dispersed in water by a neutral suspending agent. They are fine and non-dissolving drug preparations dispersed in liquids. The suspension for oral use is:
1. Emulsions: suspension of fat or oil in water with the help of an emulsifying agent. Oil particles are coated with emulsifying agents so that they do not aggregate as the interfacial tension between the oil and water decreases. A stable suspension is thus produced.
2. Gels are colloidal aqueous suspensions of hydrated inorganic materials.
3. Magmas are massive suspensions of poorly soluble materials in water They are also called ‘Duh S’ as they are white in colour. Magma and gel are similar but the particles suspended in magma are larger. Magmas thus tend to separate on standing and require a ‘shake well before use’ label.
4. Mixtures are preparations in which the drug or drugs are in solution or suspension for oral administration.
Spirits or essences are concentrated alcoholic solutions of volatile substances. Dissolved substances can be solid, liquid or gaseous. Most spirits contain 5 – 20% of the active ingredient. Volatile oily spirits are prepared by diluting 10 volumes of oil with 90 volumes of alcohol, and coloring matter may also be added.
Many spirits are used as flavoring agents. Extractive preparations are made from herbal medicines and contain the active principles in a hydroalcoholic solvent called masal. Tinctures are alcoholic or hydroalcoholic preparations of herbal medicines.
