Suspension, type of suspension, interracial property of suspended particles

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Suspension , types of suspension, difference between flocculated and deflocculated suspension and interfacial properties of suspended particles

1. DEPARTMENT OF PHARMACEUTICAL SCIENCES, MDU ROHTAK Physical Pharmaceutics Assignment Suspension and interfacial Properties of suspended particle Presented by Dheeraj B.Pharm.4 th sem Roll no: 1431

2. A pharmaceutical suspension is a coarse dispersion in which insoluble solid particles are dispersed in a liquid medium. An acceptable suspension possesses certain desirable qualities inlcuding the following: Solid particles should not settle rapidly. Settling particles do not form cake. Particles easily disperse when container is shaken Not be too viscous to pour freely from the bottle. For external suspensions, product spread easily over the affected area,Must not be so mobile that it runs off the surface to which it is applied. It must have an acceptable color and odor . Suspensions

3. Product /ingredients are easily be obtained from the vehicle and bottle. Physical stability of suspensions may be defined as the condition in which the particles do not aggregate and in which they remain uniformly distributed throughout the dispersion. The large surface area of the particles that results surface free energy that makes the system thermodynamically unstable. Particles are highly energetic and tend to regroup in such a way as to decrease the total area and reduce the surface free energy. The particles in a liquid suspension therefore tend to flocculate, that is, to form light, fluffy conglomerates that are held together by weak van der Waals forces.

4. Types of suspension Flocculated suspension Deflocculated suspen sion Suspension in which particles of suspension has undergone flocculation and form a aggregated cake or group. Unpleasant in appearance. Rate of sedimention is fast. Bioavailabiolity is comparatively less. Sediment paritcles are lossely packed. Suspension in which paritlces of suspensions has not undergone flocculation but exist as single or different identity. Pleasant in appearance as particles are uniformly distributed. Rate of sedimention is slow. Bioavailabillty is relatively high. Sediment particles are closely packed.

5. Work must be done to reduce a solid to small particles and disperse them in a continuous medium. Particles may form cake under certain conditions. Caking is the growth and fusing together of crystals in the precipitates to produce a solid aggregate. To make a good thermodynamic stable suspension: An increase in the work, W, or surface free energy,increasing the total surface area, A, is given by G = γ SL · A where γ SL = interfacial tension between the liquid medium and the solid particles. To approach a stable state, the system tends to reduce the surface free energy; equilibrium is reached when G = 0. INTERFACIAL PROPERTIES OF SUSPENDED PARTICLES

6. A suspension of insoluble particles, then, usually possesses a finite positive interfacial tension, and the particles tend to flocculate. forces at the surface of a particle affect the degree of flocculation and agglomeration in a suspension. Forces of attraction are of the London–van der Waals type; the repulsive forces arise from the interaction of the electric double layers surrounding each particle. the repulsion energy is high, the potential barrier is also high, and collision of the particles is opposed. The system remains deflocculated, and, when sedimentation is complete, the particles form a close-packed arrangement with the smaller particles filling the voids between the larger ones. INTERFACIAL PROPERTIES OF SUSPENDED PARTICLES

7. The repulsion energy is high, the potential barrier is also high, and collision of the particles is opposed. The system remains deflocculated. Repulsive energy is low, potential energy barrier is low , so collision of particles take place and system shows the property of flocculated suspension. Potential energy curves for particle interactions in suspension.

8. Those particles lowest in the sediment are gradually pressed together by the weight of the ones above; the energy barrier is thus overcome, allowing the particles to come into close contact with each other. To resuspend and redisperse these particles, it is again necessary to overcome the high-energy barrier. Because this is not easily achieved by agitation, the particles tend to remain strongly attracted to each other and form a hard cake. When the particles are flocculated, the energy barrier is still too large to be surmounted, and so the approaching particle resides in the second energy minimum, which is at a distance of separation of perhaps 1000 to 2000 A. INTERFACIAL PROPERTIES OF SUSPENDED PARTICLES

9. 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. Oxy tetracycline 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. E.g. penicillin procaine Vaccines as a immunizing agent are often formulated as suspension. E.g. Cholera vaccine. Application of Suspensions

10. X-ray contrast agent are also formulated as suspension . eg: Barium sulphate for examination of alimentary tract. Some Pharmaceutical suspensions are 1. Antacid oral suspensions 2. Antibacterial oral suspension 3. Dry powders for oral suspension (antibiotic) 4. Analgesic oral suspension 5. Anthelmentic oral suspension 6. Anticonvulsant oral suspension 7. Antifungal oral suspension Applications of Suspension

11. CONCLUSION Suspension be the solution in which insolube solid paarticles are disperse in the solvent with the help of suspending agents, wetting agent etc. Suspension is two types based on flocculation property: Flocculated suspension : suspension in which particles form a aggregation and have low repulsive and potenial energy. Deflocculated suspension : suspension in which particles exist as single identity and do not forom aggregates and having high replusive and potential energ y. To find the interfacial tension between the particles, we use the formula G = γ SL · A Suspension be the solution are mostly used to mask any bitter drug taste or undesirable property of drug like taste,smell,colour etc.

12. Resources Martin A., Physical Pharmacy physical chemical principles in the pharmceutical sciences,B.I.Waverly pvt.ltd., page number:477-480. Subrahmanyam CV, textbook of physical pharmaceutics, vallabh prakashan,page number:366-375. Shashikant A., Barhate S., Bendenumble B., a textbook of physical pharmaceutics – II,Nirali prakashan , page number : 3.1 -3.7 Ansel C., Allen L.V., Popovich N.G. Eighth edition “Disperse systems” Pharmaceutical Dosage Forms & Drug Delivery Systems, Lippincott Williams and Wilkins, Philadelphia 2005, Page No. Page No. 387-389, 398. Cooper & Gun, Sixth edition, “Dispersed system” Tutorial Pharmacy, Page No. 75-78.