1. Many people have difficulty in swallowing solid dosage forms and therefore require the drug to be dispensed in a liquid. If the drug is insoluble or poorly soluble in a suitable solvent their formulation as a suspension is usually required.

2. The degradation of a drug in the presence of water may also preclude its use as an aqueous solution in which case it may be possible to synthesize an insoluble derivative which can be then be formulated as suspension, eg., oxytetracyline hydrochloride is hydrolyzed rapidly in aqueous solution.

3. The prolonged contact between the solid drug particles and dispersion medium can reduce the efficiency of some drugs e.g. Ampicillin. The pharmacist makes the product up to volume with water immediately before issue to the patient. Shelf-life of product is 7 days at room temperature and 14 days at refrigerator.

4. Some materials are required to be present in the gastrointestinal tract in a finely divided form, their formulation as suspensions will provide the desired high surface area e.g., kaolin, magnesium carbonate, magnesium trisilicate etc. used for the adsorption of toxins or to neutralize excess acidity.

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5. The adsorption properties of fine powders are also used in the formulation of some inhalations. The volatile components of menthol and eucalyptus oil would be lost from solution very rapidly during use. Prolonged release suspension would contain volatile ingredients adsorbed on light magnesium carbonate.

6. Tastes and odors of drugs are more noticeable if in solution than in an insoluble form e.g., paracetamol suspensions are particularly more suitable for children as compared to paracetamol elixir. Insoluble chloramphenicol palmitate is successfully formulated in the form of suspension.

7. Suspension of drugs can also be formulated for topical application e.g., Calamine lotion.

8. Suspension can also be formulated for parenteral administration to control the rate of absorption of the drug e.g., depot, implants.

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9. Vaccines are often formulated as suspension for induction of immunity. They may consist of dispersions of killed micro-organisms as in Cholera vaccine, Diphtheria and Tetanus vaccines.

10. X-ray contrast media are also formulated in the form of suspension e.g., barium sulphate suspension for alimentary tract examination.