1. Kh. Sadique Faisal Asst. Lecturer Northern University Bangladesh
Suspension
Kh. Sadique Faisal
Asst. Lecturer
Northern University Bangladesh

2. Suspension
A coarse suspension is a dispersion of finely divided, insoluble solid particles (the disperse phase) in a fluid (the dispersion medium or continuous phase).Most pharmaceutical suspensions consist of an aqueous dispersion medium, although in some instances it may be an organic or oily liquid. A disperse phase with a mean particle diameter of up to 1 µm is usually termed a colloidal dispersion, and includes such examples as aluminium hydroxide and magnesium hydroxide suspensions. A solid in liquid dispersion, in which the particles are above colloidal size, is termed a coarse suspension.

3. Properties of an ideal suspension
Homogenous distribution:- The product must remain sufficiently homogenous for at least at the period between shaking the container and removing the required amount.
Nature of Sedimentation:-The sedimentation or creaming produced on storage, if any, must be easily resuspened by moderate agitation of the container.
Thickness or Viscosity :-The product may be required to be thickened or viscous in order to reduce the rate of settling of the particles. The resulting viscosity must not be so high that removal of the product from the container and transfer to the site of application is difficult.
Particle size :-Any suspended particles should be small and uniformly sized in order to give a smooth, elegant product, free from a gritty texture.

4. Classification
Based On General Classes Oral suspension Externally applied suspension Parenteral suspension Based On Proportion Of Solid Particles Dilute suspension (2 to10%w/v solid) Concentrated suspension (50%w/v solid) Based On Electrokinetic Nature Of Solid Particles Flocculated suspension Deflocculated suspension Based On Size Of Solid Particles Colloidal suspension (< 1 micron) Coarse suspension (>1 micron) Nano suspension (10 ng)

5. Advantages
· Suspension can improve chemical stability of certain drug.
E.g.Procaine penicillin G
· Drug in suspension exhibits higher rate of bioavailability than other dosage forms.
bioavailability is in following order,
Solution > Suspension > Capsule > Compressed Tablet > Coated tablet
· Duration and onset of action can be controlled.
E.g.Protamine Zinc-Insulin suspension
· Suspension can mask the unpleasant/ bitter taste of drug.
E.g. Chloramphenicol

6. Disadvantages
· Physical stability,sedimentation and compaction can causes problems.
· It is bulky sufficient care must be taken during handling and transport.
· It is difficult to formulate
· Uniform and accurate dose can not be achieved unless suspension are packed in unit dosage form

7. Applications
· Suspension is usually applicable for drug which is insoluble or poorly soluble. E.g. Prednisolone suspension
· To prevent degradation of drug or to improve stability of drug.
E.g. Oxytetracycline suspension
· To mask the taste of bitter of unpleasant drug. E.g. Chloramphenicol palmitate suspension
· Suspension of drug can be formulated for topical application e.g. Calamine lotion
· Suspension can be formulated for parentral application in order to control rate of drug absorption.
· Vaccines as a immunizing agent are often formulated as suspension. E.g. Cholera vaccine