Formulation of suspensions Flocculating agents Suspending/ thicking agents Wetting agents Dispersing agents Preservatives Organoleptic additives

Flocculated Deflocculated Particles form loose aggregates and form a network like st. Rate of sedimentation is high & rapid Sediment is loosely packed and doesnot form hard cake Particles exist as separate entites Rate of sedimentation is slow Sediment is slowly formed Sediment is closely packed and a hard cake is formed

Flocculated Deflocculated Sediment is easy to redisperse Suspension is not elegant in appearance Floccules stick to the side of the bottles Sediment is difficult to redisperse Suspension is elegant in appearance Do not stick to the side of the bottle.

Flocculating agents Agents used for the uniform distribution of particles. Surfactants-Sodium lauryl sulphate,sodium dioctyl sulpho succinate,tweens spans,carbowaxes Protective colloids- Accacia,bentonite,tragacanth

Suspending agents Agents used to suspend the particles and to increase the viscosity of the continuous phase eg. Acacia,tragacanth, sodium alginate,methyl cellulose, carboxy methyl cellulose,gelatin

Wetting agents Wetting agents are substances which reduce the interfacial tension between the solid particles and the liquid medium. Eg.alcohol in tragacanth mucilage,glycerin and glycerol in sod.Alginate/bentonite,polysorbates

Wetting Wetting agent

Preservatives Preservatives are agents used to prevent microbial growth in suspensions Wide range of organisms,phycially and chemically stable Non toxic & compatible Eg- benzoic acid,sodiun benzoate, methyl paraben

Organoleptic additives Agents used for colouring,sweetening or flavouring purposes Compatible with other ingedients

Preparation of Suspensions Requirements /ingredients The drug/Particle size Wetting agents Flocculating agents Agents to control viscosity/suspending agent Flavoring/coloring/sweeting agent Preservatives

Preparation of suspensions In the preparation of suspensions characteristic of the dispersed (drug particles) and dispersion media are important. If the dispersed phase has an affinity for the vehicle can be easily wetted. If not have a tendency to clump together or float on the vehicle. Such cases powder must be wetted to make it more penetrable by the dispersion media

Commonly used wetting agents Tragacanth mucilage in alcohol Sod.alginate/bentonite in glycerin/glycols Polysorbates-tweens Sod.lauryl sulphate,Sod.dioctyl sulpho succinate Increase the affinity of the particles for the surrounding medium & reduce the interparticular forces

Prepn. contd The wetting agents are mixed with the particles in a mortar and pestle.Once the powder is wet the dispersion medium *is added in portions to the powder and the mixture is throughly blended before subsequent addition of vehicle. *The dispersion medium already mixed with the other ingredients proportionate to the bulk (small to large ) A portion of the vehicle is used to wash the mixing equipment free of suspension and this portion is used to bring to the final volume.

Prepn. contd The final product is then passed the blender / mixing device to ensure uniformity Examine the suspension critically and if there are foreign particles strain through muslin Suitable preservatives should be included to preserve against bacterial and mold contamination.

suspensions Advantages Insoluble drugs may be more palatable Insoluble drugs may be more stable Suspended insoluble powders are easy to sallow Easy administration of bulk insoluble powders Faster absorption Disadvantages Shake well before use Accuracy of dose is questionable Storage conditions can affect the disperse system Bulky, difficult to transport Prone for container breakage

Summary of suspensions To summarize……..

Assaignment Based on the different requirements that you have studied in the theory identify the different agents used in the preparation of calamine lotion and explain its significance