Liquid Dosage Forms

Liquid Dosage Forms, Pharmaceutics I, Unit 2, Chapter 7

1. LIQUID DOSAGE FORMS Prepared by, Shantanu Ranjan
Assistant Professor ( Dept. Of Pharmaceutics ) Nibah Institute of Pharmaceutical Sciences, Rajgir , Bihar

2. Introduction Liquid dosage forms are either meant for internal, external or parental use. It can be sub classified into monophasic or biphasic liquids. Monophasic liquid dosage form are liquid preparation containing two or more components in one phase system. It is represented by a true solution. A true solution is a clear homogenous mixture prepared by dissolving solute in a suitable solvent. Biphasic dosage forms are represented by emulsions and suspension and consist of two immiscible phases, the continuous phase being liquid. In emulsion, the dispersed phase is also a liquid while in case of suspensions; the dispersed phase consists of a finely divided solid.

3. Advantages of liquid dosage forms Faster absorption than solid dosage forms. Liquids are easier to swallow than tablets or capsules and are therefore especially suitable for children and the elderly. Drugs with large doses can be easily administered as liquid dosage form. Distribution of drug in liquid dosage forms is better than solid dosage forms.
Liquid dosage forms are more economical to produce than solid dosage forms.

4. Disadvantages of liquid dosage forms Liquids are highly susceptible to microbial contamination. Drugs are usually less stable in liquid dosage forms as compared to dosage forms like tablets, capsules and powders. Liquid preparations are usually bulky and therefore inconvenient to store and carry. Suspensions and emulsions have the added drawback that they must be thoroughly shaken to allow accurate dosing. Administration of the correct dose is less precise since it depends on the ability of the patient to measure the correct dose using a suitable measuring device such as a spoon or a dropper.

5. Excipients in liquid dosage forms Excipients/Additives are substance (other than the active medicaments) which are included during the formulation of a dosage form but do not have any therapeutic activity of their own. Additives mainly serve as an aid to drug formulation.
A number of excipients are employed during the formulation of a liquid dosage form, some of them are mentioned below: Vehicles: Provide the medium for dissolving or suspending the active ingredient. Types: Aqueous Vehicles: Examples: Purified water, aromatic water. Used in solutions, syrups, and suspensions. Non-aqueous Vehicles: Examples: Fixed oils (sesame oil, castor oil), alcohols (ethanol, glycerine). Used in parenteral formulations or poorly water-soluble drugs.

6. Excipients in liquid dosage forms Stabilizers: Protect drugs from chemical degradation. Types: Antioxidants: Prevent oxidation. Examples: Ascorbic acid, sodium bisulfite . Chelating Agents: Bind metal ions to reduce oxidative degradation. Example: EDTA. Buffers: Maintain the desired pH for stability. Examples: Citrate buffer, acetate buffer. Preservatives: Prevent microbial growth in aqueous systems. Types: Parabens: Methylparaben, propylparaben. Quaternary Ammonium Compounds: Benzalkonium chloride. Organic Acids: Benzoic acid, sorbic acid.

7. Excipients in liquid dosage forms Suspending Agents: Improve physical stability by keeping insoluble particles uniformly dispersed. Types: Natural Polymers: Acacia, tragacanth. Synthetic Polymers: Sodium carboxymethylcellulose (CMC), polyvinyl alcohol. Clays: Bentonite, veegum . Emulsifying Agents: Reduce interfacial tension between oil and water phases in emulsions. Types: Natural: Acacia, lecithin. Synthetic: Polysorbates (Tween), Span. Finely Divided Solids: Magnesium hydroxide, aluminium hydroxide. Solubilizers: Increase the solubility of poorly soluble drugs. Examples: Polyethylene glycol, cyclodextrins, surfactants (Tween 80, sodium lauryl sulfate ).

8. Excipients in liquid dosage forms Colors and Flavors: Enhance the appearance and palatability of the dosage form. Colors: Must comply with regulatory standards (e.g., FDA or CDSCO guidelines). Examples: Tartrazine (yellow), erythrosine (red), sunset yellow. Flavors: Improve taste. Examples: Orange oil, peppermint oil, vanilla. Sweeteners: Provide a sweet taste to mask bitterness. Examples: Natural: Sucrose, fructose. Artificial: Aspartame, saccharin, sucralose. Thickening Agents: Provide viscosity (e.g., xanthan gum, methylcellulose). Surfactants: Reduce surface tension for better spreading (e.g., polysorbates). Wetting Agents: Improve particle dispersion in suspensions (e.g., glycerin).

9. Excipients in liquid dosage forms THANK YOU