Advantages and Disadvantages of Suspension: Suspensions are two-phase systems consisting of finely divided solids dispersed in liquids. If the drug is insoluble or poorly soluble, a suspension may be the most suitable dosage form. The taste of drugs can be improved if they are supplied in suspension form rather than solutions. Suspensions may be formulated for oral, parenteral (intramuscular or intraarticular), or topical administration. Antibiotic granules are generally used for the preparation of suspensions in pediatric practice.
Well formulated suspensions should possess certain basic properties. The dispersed phase should settle slowly, if at all possible, and should disperse readily on shaking.
The main ingredients in a suspension are:
- a drug
- natural viscosity agents (natural gums and cellulose derivatives)
- an external medium – is usually water for oral preparations; or other polar liquids (glycerin, alcohol)
Advantages and Disadvantages of Suspension
Advantages of Suspensions
- The insoluble drug may be made more palatable (masking bitter taste). For example: Chloramphenicol.
- The insoluble drug can be prepared in a more stable manner. For example: Procaine penicillin G.
- Suspensions result in more bioavailability compared to any other dosage form. Solution > Suspension > Capsule > Compressed tablet > Coated tablet.
- Duration and onset of action can be controlled. For example: Protamine Zinc-insulin injection.
- The lotion leaves a cooling layer of medicament on the skin.
- It can be prepared for both, immediate and sustained drug release preparations.
Disadvantages of Suspensions
- Suspensions require shaking before use, to ensure uniformity of dose.
- If the suspension is not shaken well, the accuracy of the dose gets affected.
- Improper storage conditions can affect the disperse system.
- Sufficient care must be taken during handling and transport.
Applications of Suspensions
- Suspension is usually applicable for a drug that is insoluble or poorly soluble. e.g. Prednisolone syrup.
- Used to prevent degradation of drug or to remove stability of the drug. e.g. Oxytetracyclin suspension.
- Used to mask the bitter drug. e.g. Chloramphenicol palmitate.
- Used for topical applications. e.g. Calamine lotion.
- Used for parenteral applications to control the rate of drug absorption. e.g. Penicillin procaine.
- Used in vaccines as an immunizing agent. e.g. Cholera vaccines.
- Used as X-Ray contrast agent e.g. Barium sulfate for examining alimentary canal.
Difference between Flocculated and Deflocculated Suspensions
|Flocculated suspension||Deflocculated suspension|
|1. Particles exist as loose aggregates.||1. Particles exist as a separate entity.|
|2. Rate of sedimentation is high.||2. Rate of sedimentation is low.|
|3. Consists of loosely packed particles possessing a Scaffolding structure. A hard dense cake does not form and the sediment can be easily redispersed.||3. Sediment becomes very closely packed as the repulsive forces between the particles are overcome. A hard cake is formed which is difficult to redisperse.|
|4. Elegant preparations are obtained due to the uniform distribution of loosely bonded flocs.||4. Unpleasant preparations result due to the formation of sedimentation.|
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