Suspending agents
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This document discusses different types of suspending agents used in pharmaceutical formulations. It classifies suspending agents into polysaccharides, inorganic salts, and synthetic compounds. Some examples of polysaccharides agents include acacia, tragacanth, and starches. Common inorganic salts are bentonite, aluminum magnesium silicate, and aluminum hydroxide. Synthetic agents include carbomers and colloidal silicon dioxide. Suspending agents help stabilize suspensions by increasing viscosity and slowing particle sedimentation according to Stokes' law. They prevent caking and can be resuspended with agitation.
Suspending agents
- 1. SUSPENDING AGENTS AND THEIR CLASSIFICATIONS
- 2. SUSPENDING AGENTS Suspending agents also called thickening agents are used to stabilize suspensions are hydrophilic colloid i.e. substances that spontaneously form colloidal dispersions with water because of an affinity between the dispersed particles and the dispersion medium. They help in lowering the sedimentation rate of particles in suspension.
- 3. The sedimentation rate is slowed down by increasing the viscosity of liquid vehicle, and slowing down settling in accordance to stokes law. They usually prevent caking at the base of an suspension . It could be resuspendend by agitation. It is majorly used as an excipients to help active pharmaceutical ingredients stay suspended in formulation. Examples : bentonite, carbomer, tragacanth, kaolin, carboxymethyl cellulose sodium etc.
- 4. Types of suspending agents: A. POLYSACCHARIDES. B. INORGANIC SALTS. C. SYNTHETIC COMPOUNDS.
- 5. A. POLYSACCHARIDES. The official suspending agents were natural polysaccharides but nowadays semi synthetic compounds are increasingly used. Following are some examples of it: o ACACIA. o TRAGACANTH. o STARCH . o ALGINATES. o XANTHAMN GUMS.
- 6. ACACIA This is dried exudates from Acacia senegal which occurs as round ovoid colorless or white powder. It is often used as suspending agents. It is not a good suspending agent but it is only used because of its protective colloidal property. It is useful for preparation of tinctures of resinous materials that precipitate on addition of water. It is not very effective for dense
- 7. Acacia mucilage becomes acidic on storage as a result of enzymatic activity and it contains oxidase enzyme which may detoriate active ingredients. Because of stickiness acacia is rarely used externally.
- 8. TRAGACANTH It occurs as thin, white or yellowish white, ribbon like flakes. It forms viscous aqueous solutions. Its thixotropic and pseudo plastic properties make it better thickening agent than acacia and can be used externally and internally. It is stable over pH 4 to 7.5.
- 9. B . INORGANIC SALTS The following are examples of inorganic salts: Clay Bentonite Aluminum magnesium silicate Aluminum hydroxide
- 10. BENTONITE Its formula is: Al2O3.4SiO2.H2O. It is subtype of montmorillonite clays, they hydrate readily absorbing up to 12 times their weight of water particularly at elevated temperatures. The gels formed are thixotropic in nature so act as good suspending agents. It is used in concentration of 2 or 3% for external use such as calamine lotion
- 11. MAGNESIUM ALUMINUM SILICATE (VEEGUM) They are insoluble flakes that disperse and swell readily in water absorbing the aqueous phase into crystal phase. They are used in concentration of 5% both externally and internally. They are stable at pH 3.5 to 11.They are use din combination with organic thickening agents such as xanthan gum , carboxymethyl cellulose. They have high thixotropic and plasticity but presence of salts can alter these rheological properties because of flocculating effect.
- 12. C . SYNTHETICS These were introduced to over come various problems occurring from natural products. Following are its examples Carbomers. Colloidal silicon dioxide.
- 13. CARBOMERS (CARBOXYPOLYMETHYLENE) This material is totally copolymer of acrylic acid and allyl sucrose. It is used in concentration up to 0.5% for external preparations. When dispersed in water it forms acidic, low viscous solutions, when adjusted to pH between 6 to 11 becomes highly viscous.
- 14. COLLOIDAL SILICON DIOXIDE(AEROSIL) When dispersed in water they form a three dimensional network. It is used up to concentration of 4% for external use, also it is used as thickening agent for non aqueous suspension. It is obtained from silicon dioxide and is white non griffty powder. Because of fine particles it forms cake which cannot be easily redispersible.
- 15. Thank you! From SILVI SINGH Roll No.13BPH094 Semester 5 , B.PHARM