Suspension Sec 3 PDF

Suspension Sec 3 Dr Amany Salah Definition suspension may be defined as preparation containing finely divided drug particles(internal phase) distributed somewhat uniformly throughout a vehicle(external phase or suspending medium) in which the drug exhibits a minimum degree of solubility...

Suspension Sec 3 Dr Amany Salah Definition suspension may be defined as preparation containing finely divided drug particles(internal phase) distributed somewhat uniformly throughout a vehicle(external phase or suspending medium) in which the drug exhibits a minimum degree of solubility.  Or Suspensions are the biphasic liquid dosage form of medicaments in which the finely divided solid particles. The range of solid particles in suspension from 0.5 to 5.0 micron. suspensions are used in orally, parentally and also externally. They are chemically stable than solution according to the particle size of the dispersed phase, suspensions are divided into: Coarse suspension: which is a dispersion of particles with a mean diameter greater than1 µm. Colloidal suspension: Which is a dispersion of particles with a mean diameter less than 1 µm Reasons for suspension 1. If patient has a difficulty of swallowing solid dosage forms (a need for oral liquid dosage form). 2. Faster rate of dissolution and oral absorption than solid dosage forms, yet slower than solutions. 3. Drugs that have very low solubility are usefully formulated as suspensions. 4. Drugs that have an unpleasant taste in their soluble forms (e.g., chloramphenicol (soluble) vs. chloramphenicol palmitate (insoluble )).  5.To over come the instability of certain drugs in aqueous solution i.e. drugs that degraded in aqueous solution :-a-it may be possible to synthesize an insoluble derivative that can be formulated as a suspension e.g. aqueous solution of hydrochloride salt of oxytetracycline is stable for 30 days at 25c , quaternary ammonium salt which is water insoluble –very stable for at least 24 months storage  Properties of good suspension suspension should settle slowly & should be readily redispersed upon shaking of the container. The suspension is palatable (for internal used susp). Particles in suspension are small and relatively uniform in size. so that the product is free from a gritty texture (for external used susp).  Classification Based on General class →Oral Suspension e.g. Paracetamol Suspension → Externally Applied suspension e.g. Calamine lotion → Parenteral Suspension e.g. Insulin zinc suspension  Based on proportion of Solid Particles Dilute Suspension (to50% w/v solid) e.g. cortisone acetate, prednisolone acetate Concentrated Suspension (above 50% w/v solid) e.g. Zinc oxide suspension Based on Size of Particle Coarse Suspension: Suspensions having particle sizes of greater than about 1micron in diameter are called as coarse suspensions. Colloidal Suspension : Suspensions having particle sizes of suspended solid less than about 1micron in size are called as colloidal suspensions. Based on electro kinetic nature of Solid particle Flocculated Suspension Deflocculated Suspension  Flocculated Suspension flocculated system the individual particle are contact with each other to form loose aggregate & create network like structure. Rate of sedimentation is high. Sediment is loosely packed. When shaking it can be redispersed easily & reform the original suspension.  Deflocculated suspension In deflocculated system the individual particle are exist as separate entities. Rate of sedimentation is low. Sediment is tightly packed. When shaking it can not be redispersed easily & form the cake.  Problems of suspension 1- sedimentation (caking) 2- Uniform and accurate dose can not be achieved unless suspension are packed in unit dosage form. 3- It is bulky: sufficient care must be taken during handling and transport. 4- It is difficult to formulate.  Caking in suspension It is defined as the formation of a non redispersible sediment within a suspension system. CAUSES: 1. Crystal bridging & closed aggregate in formulation. 2. small changes in temperature that occurs during shelf storage lead to unexpectedly rapid caking via crystal bridging According to the Stoke's equation, the velocity of sedimentation of particles in a suspension can be reduced by: 1- decreasing the particle size. 2- by minimizing the difference between the densities of the particles and the vehicle. The density of the vehicle of a suspension can be increased by adding the following substances either alone or in combination: polyethylene glycol, polyvinyl pyrolidone, glycerin, sorbitol, and sugar. 3- by increasing the viscosity of the vehicle, the viscosity and density of any vehicle are related to each other  preparation of suspension:- 1- grinding the insoluble materials separately in the mortar 2- levitating the powder with the portion of the vehicle or by wetting agent as glycerol in case poorly wettable insoluble substance till a smooth paste formation ---------- (1) - in the other hand, all soluble ingredients are dissolved in same portion of vehicle (3/4 of total vehicle ) --------- (2) ( in this step can add other liquid ingredients, volatile liquid are to be added at last )  3- added NO (2) to the smooth paste NO (1) and mix well to give slurry (smooth cream). 4- the slurry is transformed to cylinder, THEN the mortar is rinsed with successive portion of the vehicle. 5- make up the dispersion to the final volume  Magnesium sulfate mixture ( Mistura alba) R/ Mg.sulphate 5 g. Light mg.carbonate 1 g. water to 15 ml Fiat : mist.mitte, II doses. Sig.: 30 ml. Uses:-Laxative and antacid Label:- white mixture(shake the bottle before use)  Translation factor = 30/15 = 2 So, R/ Mg.sulphate 10 g. Light mg. Carbonate 2 g. water to 30 ml Make : suspension send to 30 ml write on label : 15ml every morning  procedure 1.Weight the required amount of magnesium sulphate and magnesium carbonate 2. Dissolve magnesium sulphate (soluble solid ) in about 20-22.5 ml of peppermint water in beaker. 3. In dry clean mortar triturate magnesium carbonate ( insoluble solid ) to form a smooth paste with a little of vehicle or glycerin. 4. add the beaker content to the mortar (magnesium carbonate ) with mixing well to give slurry. 5. transfer to a measuring cylinder. 6. Rinse the mortar with successive portion of the vehicle and also transfer it to the cylinder.& then complete the required volume with the vehicle. 7. Transfer to white glass bottle.