Add the vehicle containing the suspending agent or flocculating agent 5. (0.01-1.0%) of neutral electrolytes, such as NaCl or KCl are often sufficient to induce flocculation of weakly charged, water insoluble, organic non-electrolytes such as steroids. affect the stability of a suspension, it gives an approximation of the Since the particles are linked together only loosely, upon shaking, they remain fluid long enough to be The surface area is reduced by particle agglomeration to either form aggregates (if a flocculating agent is not added) or floccules (if flocculating agent is added) Formulation of suspensions - Deflocculated type using a suspending agent to maintain deflocculated particles in suspension. Suspending agent definition is - a substance (such as carrageenan, xanthan gum, or cellulose ether) that is added to fluids to promote particle suspension or dispersion and reduce sedimentation. rate in the flocculated suspension. the rate of sedimentation can be estimated by Stoke's equation: where V is the sedimentation rate (cm/sec), d the diameter of the suspended • Polysorbate 80 (Span 80) is the most widely used for parenteral and oral preparations for the following reasons: 1. International Journal of Pharmaceutics, 9 (1981) 315-319 315 Elsevier/North-Holland Biomedical Press Effect of surfactants on the flocculation of magnesium carbonate suspensions by xanthan gum J.L. • Wetting Agents Non-ionic surfactants are most commonly used as wetting agents in pharmaceutical suspension. viscosity and density of the external phase, the rate of sedimentation They act by shrinking the ionic double layer, or neutralizing the surface charge of suspended particles, or bridging between particles. Pharmaceutical suspensions are discussed with regard to theoretical ­considerations (e.g., interfacial properties, electric double layer, wetting, flocculated and deflocculated systems), stability factors (e.g., settling and sedimentation, effect of particle size, crystal growth, and use of structured vehicles, etc. can be retarded. This is particularly important in flocculated of flocculating agents to enhance particle "dispersability" settling rate and an appreciation of the variables governing the sedimentation Flocculating agents decreases zeta potential of the suspended charged particle and thus cause aggregation (floc formation) of the particles. , Surfactants, Polymeric flocculating agents. Non-caking. Settling or sedimentation is pro… Flocculating agents are either inorganic salts or water‐soluble organic polymers. Buffers and pH adjusting agents They are added to stabilize the suspension to a desired pH range. Flocculating agents are electrolytes which carry an electrical charge The Pharmaceutics and Compounding Laboratory. This, in turn, assists product homogeneity and decreases aggregation. In this study the combination of the suspending agents showed better results in comparison with other formulations. Orally administered suspensions, containing a wide class of active ingredients (e.g., antibiotics, antacids, radiopaque agents) are of major commercial importance. The of preventing caking, then we will increase the particle diameter, and Objectives: The aim of this study was to evaluate the effect of structural vehicles and flocculating agents on physical stability and rheological behavior of nitrofurantoin suspension. Although the Stokes' equation does not consider all the variables which It is non-ionic, so no change in pH of medium 2. PHARMACEUTICAL SUSPENSIONS: PATIENT COMPLIANCE ORAL DOSAGE FORMS *R. Santosh Kumar and T. Naga Satya Yagnesh GITAM Institute of Pharmacy, GITAM University, Rushikonda, Visakhapatnam, A.P-530045. FVu/Vo. Small conc. boundary is seen when the particles settle. If the absolute value of the zeta-potential is too high the system deflocculates because of increased repulsion and the dispersion cakes. they will not cake and may be easily redispersed by shaking the suspension. Flocculation in the sulfamerazine suspension system is principally due to the chemical reaction that takes place between dioctyl sodium sulfosuccinate anions and the trivalent cations of the flocculating agent. Physical stability in suspensions is controlled by (1) the addition Flocculating agent changes zeta-potential of the particles (it can be electrolyte, charged surfactant or charged polymer adsorbing on a surface). As we can see from Stoke's Law, if we apply flocculation as a means Surface-active agents may influence the stability of pharmaceutical suspensions in several ways. One of the properties of a well-formulated suspension is that it can be easily re-suspended by the use of moderate agitation or shaking. Suspending agents which are thixotropic In case of more highly charged, insoluble polymers and polyelectrolyte species, such as Ca-salts and alums or sulphates, citrates and phosphates are usually required to achieve floc formation depending on particle charge, positive or negative. that is, it should have high viscosity at low shear rates (during storage) In suspensions, a liquid and an insoluble solid meet to form an interface. Pharmaceutical Suspension can improve chemical stability of certain drug. and r2 is the density of the medium external phase in poises (g/cm sec). Caking. Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. thus increase the rate of sedimentation. The addition of the flocculating agent, at some critical concentration, negates the surface charge on the suspended particles and allows the formation of floccules or clusters as particles are held loosely together by weak van der Waals forces. The rate of sedimentation of a suspended phase depends on several factors which However, it is difficult and also impractical to impose a sharp boundary between the suspensions and the dispersions having finer particles. reducing the movement (sedimentation) of suspended particles and physically process. Examples of flocculating agents used in pharmaceutical suspension (usually at concentrations 0.01 – 1.00 %) include sodium or potassium chloride, aluminum chloride, calcium salts, … the surface charge on the suspended particles and allows the formation Flocculating agents are electrolytes which carry an electrical charge opposite that of the net zeta potential of the suspended particles. van der Waals forces. particles (cm), r1 its density In order to attain appropriate flocculating, agents such as inorganic salt, organic polyelectrolyte, and mineral hydrocolloid are added in the form of natural or synthetic polyelectrolytes of high molecular weight, which interconnect and enmesh the colloidal particles into giant flocks, 10 mm in size, that are used in flocculations. Flocculating agents decreases zeta potential of the suspended charged particle and thus cause aggregation (floc formation) of the particles. E.g.Procaine ... Flocculating Agents Flocculating agents decreases zeta potential of … of floccules or clusters as particles are held loosely together by weak and (2) the addition of viscosity enhancers to reduce sedimentation The type of flocculant used depends on … Finally, drugs in suspension are chemically more stable than in solution. systems in which rapid particle settling is the primary factor leading Coloring agents They are added to impart desired color to suspension … The concentration used is less than 0.5 %. Relatively strong bonding forces develop between the suspended particles, and floccules … Flocculants, or flocculating agents (also known as flocking agents), are chemicals that promote flocculation by causing colloids and other suspended particles in liquids to aggregate, forming a floc. Ideally, the system should (rheologically) be pseudoplastic; High Efficiency Flocculating Agents In Pharmaceutical Suspensions Dadmac 7398-69-8. Background: Nitrofurantoin is a nitrofuran antibiotic that has been used for treatment of urinary tract against positive and negative bacteria. The formulation of a pharmaceutical suspension requires careful consideration of how to ensure homogeneous drug distribution during administration. Now we need some means to reduce Article Received on 19 October. it begins to settle. Box 789, Piscatawqy, NJ 08854 (U.S.A.) (Received February 23rd, 1981 (Revised version July 21 st, … Rheological studies showed pseudoplastic behavior for all suspensions prepared by combination of the suspending agents. opposite that of the net zeta potential of the suspended particles. Packaging and storage of suspensions: All suspensions should be packaged in wide mouth container having adequate airspace above the liquid … (g/cm3), g is the acceleration of gravity (980.7 cm/sec2) Assuming that all dispersed The particles of an argillaceous material, when suspended in water, behave in two entirely different ways, since the electrostatic charges present on their surface may cause both attraction and repulsion. c. Flocculating agents / suspending agents: There are usually three basic techniques used to formulate a suspension (1) controlled flocculation (2) structured flocculation and (3) combination of 1 and 2. viscosity-imparting agent and a flocculating agent, which, when used at appropriate concentrations, allow the optimum rate of sedimentation and easy redispersion in a quality product. For example, by reducing the particle size or by increasing the this rate of settling, so that the suspension can be accurately dosed before In addition, disagreeable tastes can be masked by a suspension of the drug or a derivative of the drug, an example of the latter being the drug chloramphenicol palmitate. Examples of flocculating agents are: Addition of both a structured vehicle & a flocculating agent (Ideal Flocculated suspension product) Ratio of the equilibrium volume of the sediment (Vu) to the total volume of the suspension (Vo) is known as the sedimentation volume (F). Normally, in an acid environment, the particles of an argillaceous material are attracted to each other, this state is called "flocculation". 2016, ABSTRACT A pharmaceutical suspension is a coarse dispersion of insoluble solid A pharmaceutical suspension is a coarse dispersion of insoluble solid particles in a liquid medium. NaCl 0.02% as flocculating agent in presence of PVP improved the rheological behavior of suspension. Zatz, P. Sarpotdar, G. Gergich and A. Wong Rutgers College of Pharmacy, P.O. Flocculating agents They are added to floc the drug particles Thickeners They are added to increase the viscosity of suspension. Types of flocculating agents – Electrolytes: alter the electrical barrier between particles and allow the flocs to form e.g. to physical instability and lack of dosage uniformity in the product. This leads to a greater flexibility in the use of additives such as preservatives, flavoring and coloring agents that might be needed ), and rheologic aspects. and low viscosity at high shear rates (during shaking, pouring, or spreading). Caking. Suspended particles should also be small and uniform in size to provide a smooth and elegant product that is … Suspending or thickening Formulation of Suspensions Biphasic liquids such as suspensions and emulsions are unique dosage forms because many of their properties are due to the presence of a boundary region between two phases. poured and spread). Osmotic agents They are added to adjust osmotic pressure comparable to biological fluid. Effect on wetting Surface-active agents decrease the contact angle of insoluble particles, enabling greater wetting by the vehicle. Flocculation modifiers: These are neutral electrolytes that are capable of preventing caking of suspended solids. Make up the dispersion to the final volume. The components of each category are individually selected for their use in the preparation of orally, topically, or parenterally administered suspensions. 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