Suspending Agent Research Articles

Formulation Development and Stability Studies of Aqueous Metronidazole Benzoate Suspensions Containing Various Suspending Agents

ABSTRACTMetronidazole is a synthetic antibacterial and antiprotozoan agent. Crystallization occurs in aqueous metronidazole benzoate suspensions caused by an anhydrate to monohydrate conversion. This study aimed to develop an aqueous metronidazole benzoate suspension that does not exhibit this hydration and the accompanying crystal growth. Four suspending agent systems were evaluated. Xanthan gum and Avicel® RC-591 (a combination of microcrystalline cellulose and carboxymethylcellulose sodium) were found to be the suspending agents that resulted in optimal formulation properties. Monohydrate formation did not occur in product containing Avicel® RC-591, indicating that suspending agents may exert a positive effect on metronidazole benzoate suspension stability.

Development of Suspending Agent from Sodium Carboxymethyl Mungbean Starches

ABSTRACTThree sodium carboxymethyl mungbean starches (SCMMSs) were selected, based on the physicochemical profiles and evaluated as potential pharmaceutical suspending agent in comparison with a sodium carboxymethyl tapioca starch and other five commercial suspending agents. Ibuprofen suspension was employed as a model formulation with 0.5, 1.0, and 2.0% w/v of suspending agents. Evaluation parameters included the determination of sedimentation volume ratio, redispersibility, viscosity and rheological properties and content uniformity studies. The results revealed that a high-viscosity modified mungbean starch, MMS-M-04, possessed suitable properties as a suspending agent and, at 1% concentration, was as effective as sodium carboxymethylcellulose and xanthan gum, two most-commonly used suspending agents. This modified starch could be further developed and employed as a new commercial suspending agent in the pharmaceutical industry.

Water dilutable secondary stabilisers in suspension polymerisation of vinyl chloride monomer

One of the continuing trends in the development of superior quality suspension poly(vinyl chloride) (sPVC) resin has been the need to impart higher grain porosity, facilitating improved vinyl chloride monomer removal and faster, more uniform, plasticiser uptake. To achieve this, PVC producers have adopted the use of specific secondary suspending agents, traditionally in the form of low hydrolysis, low molecular weight poly(vinyl acetate) (PVAc).It is well known that low hydrolysis PVAc is insoluble in water, and as such must be supplied as alcohol or alcohol rich solutions, typically in methanol. The use of methanol presents safety and environmental hazards relating to its particular toxicity and flammability. These concerns led to the development, during the 1980s, of water based secondary suspending agents, with a low methanol content, typically at 55% hydrolysis. These partially hydrolysed PVAcs remained for a long time the optimum hydrolysis at which a stable, aqueous product could be supplied, while imparting good PVC grain porosity. Nevertheless, in certain sPVC formulations, aqueous based 55% hydrolysed secondary suspending agents were failing to achieve the same high porosity levels as the solvent based systems, which typically had hydrolysis levels below 50%.The recent development of a lower hydrolysis, water soluble, fully dilutable grade, named Alcotex WD30, has provided an ideal solution, giving all the advantages of both secondary systems. This has been achieved by the ionic modification of the polymer, imparting superior water solubility, and allowing the production of a stable, aqueous partially hydrolysed PVAc at less than 50% hydrolysis. It has been demonstrated, using experimental design software, that such a water based, modified secondary, of 45–50%hydrolysis, is anoptimum product for producing high porosity PVC, with an acceptable grain size, in conjunction with a 72·5% hydrolysed PVAc as the primary suspending agent. The actual molecular weight of the polymer, or the degree of ionic modification required to aid the solubility of the polymer in water, has a negligible effect on the PVC properties.

院内製剤ジンクピリチオンローションの調製と物理学的特性

In order to treat psoriasis, many kinds of drugs are administered systemically and topically. However, the topical admimistration of drugs is preferred to the systemic administration because the former can occasionally cause serious side effects. Zinc Pyrithione (ZPT), which is recognized as an active ingredient in a major anti-dandruff shampoo, was introduced as a new antipsoriatic agent. In this study, ZPT lotions as a hospital preparation were prepared for topical administration.Hydroxypropylcellulose-H (HPC), sodium-polyacrylate (PANA) and carmellose sodium (CMC) were used as a suspending agent of 0.5% ZPT lotion. The following physical characteristics, the viscosity, the osmotic pressure, the sedimentation, the microscopic view and the dispersion were investigated in each ZPT lotion containing different suspended agents.The viscosity of the ZPT lotion with HPC and CMC increased with the additive ratio of these suspended agents. On the other hand, the viscosity of the ZPT lotion with PANA increased logarithmically with its additive ratio. The low osmotic pressure of each lotion was expected to be less irritable in clinical application. When ZPT lotions were stored at room temperature for 14 days, the lotion with HPC or CMC showed free sedimentation and caking of the particles. In contrast, the lotion with PANA showed a growth of particles by a microscopic analysis and coagulated sedimentation by macroscopy. These phenomena may be due to the ionic intensity of the solution and the interaction between ZPT particles. The dispersion time of ZPT lotions with PANA was shorter than those with HPC or CMC.Based on our findings, 0.2% PANA was found to be preferable to HPC and CMC as the suspended agent in ZPT lotion.

Preliminary Evaluation of Shilajit as a Suspending Agent in Antacid Suspensions

The efficacy of shilajit, a gummy exudate of the plant Styrax officinalis Linn (Family: Styraceae), was evaluated as a suspending agent for the formulation of antacid preparations. Shilajit produced effects on sedimentation volume similar to those produced by sodium carboxymethyl cellulose (CMC), but at lower concentrations. It induced better flocculation with a moderate increase in viscosity compared to CMC. It did not interfere with the acid-consuming capacity of the suspensions.

A Comparative Evaluation of Five Common Suspending Agents Used in Drug Safety Studies

Suspensions of three drugs at three concentrations (0.1, 1.0 and 10.0% w/w), prepared using five common suspending agents, have been evaluated for their suitability in drug safety studies. The suspending agents (methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose and gum tragacanth) were used in gels of similar viscosity. Sodium carboxymethylcellulose and hydroxyethylcellulose proved to be unsatisfactory in that drug assays for six of the nine suspension samples were outside the demanding limits set (±5% of theoretical). Methyl cellulose and hydroxypropylmethylcellulose were both considered to be equally satisfactory as the agent of first choice. Gum tragacanth performed slightly less well with the cationic drug used than the cellulose based agents. It is concluded that suspending agent gels should be of adequate viscosity to obtain satisfactory suspensions and that anionic suspending agents with the potential to interact with drugs are best avoided.

Xanthan Gum—A Lyotropic, Liquid Crystalline Polymer and its Properties as a Suspending Agent

Abstract A variety of polysaccharides have been used in drilling fluids,1–4 and some of these polymers have been studied in tertiary recovery. Of particular interest in both these areas has been xanthan gum, the extracellular polysaccharide produced by Xanthomonas campestris, because of its relatively stable viscosity properties as a function of salt concentration, pH, temperature, and shear degradation. Indeed, no synthetic polymer or any other commercially available, naturally occurring polymer, or polymer derivative has been able to duplicate the solution behavior of xanthan gum. During a study of xanthan gum's ability to suspend barium sulfate, it appeared that xanthan gum in aqueous solution at relatively low concentrations could have lyotropic liquid crystalline behavior. Behavior of this type has been noted for other biopolymers5 and recently has been demonstrated for various cellulose derivatives.6–10 An anisotropically ordered polymer solution would be extremely difficult to reproduce synthetically but could explain most of the unique properties of xanthan solutions. To test the possibility that xanthan gum could have liquid crystalline order, a variety of xanthan solutions of various polymer concentrations in the presence and absence of various salts were studied under a polarized light microscope (100X). With solutions from 2 to 10% (wt/vol) xanthan gum in distilled water at room temperature, birefringent, ordered domains were observed at 10% concentration, with a decrease in birefringence as the polymer concentration decreased. At 2% concentration, no birefringence was observed, indicating the apparent area of change from an isotropic to an anisotropic phase. This point appears to occur at 2.9% by optical determination. In fact, this value could be considerably lower as revealed by other techniques for anisotropic xanthan solutions.8–10 For the 10% solution of xanthan gum, heating in a roller oven at 150°F (66°C) for 2 hours did not diminish the birefringence. Similarly, when a 10% xanthan gum solution was prepared in 10% KCI and in 33% CaCl2 solutions, birefringence was not decreased.

Preparation and magnetic filtration of polyacrylamide gels containing covalently ommobilized proteins and a ferrofluid

Abstract Adenylate kinase, acetate kinase, and horseradish peroxidase have been immobilized covalently in good yields (20–90%) by free radical copolymerization of acrylamide, N,N'-methylenebisacrylamide, and N-acryloxysuccinimide, in a solution containing enzyme and enzyme-protecting reagents (substrates, DTT). To establish the sequence of events responsible for the formation of these enzyme-containing gels, rates for the reactions of N-acryloxysuccinimide and N-acetoxysuccinimide with oxygen-, nitrogen-, and sulfur- containing nucleophiles were determined. These data suggest that the rate of acylation of lysine ϵ-amino groups by N-hydroxysuccinimide-active esters is such that acylation and polyacrylamide gel formation are concurrent in the experiment procedures used. The yield of active, covalently-immobilized enzyme obtained by this procedure depends critically on active ester concentration and pH. To facilitate separation of these enzyme-containing gels from suspension, a ferrofluid — a surfactant-stabilized magnetite colloid — has been entrapped in them. The resulting magnetic gels can be manipulated using either conventional magnetic filtration and containment techniques, or more effective high-gradient procedures. Suspension polymerization can be used to produce spherical magnetic beads. The choice of suspending medium (a thixotropic carbon tetrachloride—n-heptane—silanized fumed silica mixture) and surface active agent (lecithin) are crucial to the success of this polymerization procedure.

The effect of some biphenyl solubilizing and suspending agents on biphenyl 4-hydroxylase of rabbit liver microsomes

The effects of ethanol, acetone, dimethylsulfoxide (DMSO), polyoxyethylene sorbitan monooleate (Tween 80), polyoxyethylene sorbitan monolaurate (Tween 20), Triton X-100, and carboxymethyl cellulose (CMC) on the kinetics of biphenyl 4-hydroxylase of rabbit liver microsomes were investigated in an attempt to find a substrate-solubilizing or suspending agent (carrier) which was itself a non-effector of the mixed-function oxidase. The effects of these carriers on the activities of NADPH-cytochrome P-450 reductase, NADPH-cytochrome c reductase, and cytochrome P-450 content were also investigated. Ethanol and DMSO inhibited biphenyl 4-hydroxylase and NADPH-cytochrome P-450 reductase. Acetone inhibited the hydroxylase uncompetitively at concentrations which appeared to stimulate NADPH-cytochrome P-450 reductase. All of the detergents inhibited biphenyl 4-hydroxylase although only Triton X-100 markedly affected the reduction of cytochrome P-450. The interaction of Tween 80 with the hydroxylase gave rise to non-linear Lineweaver-Burk plots although at high concentrations of biphenyl or low concentrations of the detergent the inhibition appeared to be competitive. Biphenyl caused a 2–3-fold stimulation of NADPH-cytochrome P-450 reductase, but in the presence of Tween 80 the stimulation was absent. Since V of biphenyl 4-hydroxylase in the presence of Tween 80 was not significantly different from V in its absence it would appear that the reduction of cytochrome P-450 was not ratelimiting. Of all the carriers studied only CMC was without effect on all aspects of microsomal electron transport investigated. As far as biphenyl 4-hydroxylase is concerned, CMC appears to be the most suitable substrate carrier.

Materials

Attagel 50 is a processed form of the mineral attapulgite, and can be used in both aqueous and organic systems as a suspending, thickening or thixotropic agent. Typical uses are as a suspending and sag control agent in adhesives, plastics and sealants, as a suspending and flatting agent in paints, and as a stabilising or thickening agent in emulsions.

Polyethylene Oxide Water-Soluble Resin as a Suspending Agent for Calamine Lotion

Polyethylene Oxide Water-Soluble Resin as a Suspending Agent for Calamine Lotion

Experiences with Fumed Silicon Dioxide as a Suspending Agent

Experiences with Fumed Silicon Dioxide as a Suspending Agent

Colloidal Magnesium Aluminum Silicate as a Suspending Agent

Colloidal Magnesium Aluminum Silicate as a Suspending Agent