Methylcellulose, preparation

Laxatives Bulk formers Polycarbophil, psyllium, and methylcellulose preparations. Citrucel, Fibercon, Konsyl, Metamucil, Perdiem, The safest laxatives for chronic use include the bulk formers and stool softeners. Saline laxatives and stimulants may be used acutely but not chronically (see text). Bulk formers hold water and expand in stool, promoting peristalsis. 

Determination of the Viscosity of Methylcellulose Prepare a 2% solution of methylcellulose or other cellulose derivative, by weight, as directed in the monograph. Place the solution in the proper viscometer and determine the time, f, required for the solution to flow from the upper mark to the lower mark in orifice tube B. Separately determine the specific gravity, d, at 20720°. Viscosity, V = Kdt. 

Dry films of methylcellulose prepared in the presence of dimethylol urea (0.05—0.2% w/w) have been shown to exhibit a faint maximum of tensile strength and elongation at break, reflecting formation of a very widely spaced network. " Further increasing the concentration of dimethylol urea resulted in a decrease in tensile strength. 

Oral contrast 1000-1500 ml water or flavoured methylcellulose preparation Hypotonia 20 mg scopolamine intravenously... 

At X-ray fluorescence analysis (XRF) of samples of the limited weight is perspective to prepare for specimens as polymeric films on a basis of methylcellulose [1]. By the example of definition of heavy metals in film specimens have studied dependence of intensity of X-ray radiation from their chemical compound, surface density (P ) and the size (D) particles of the powder introduced to polymer. Have theoretically established, that the basic source of an error of results XRF is dependence of intensity (F) analytical lines of determined elements from a specimen. Thus the best account of variations P provides a method of the internal standard at change P from 2 up to 6 mg/sm the coefficient of variation describing an error of definition Mo, Zn, Cu, Co, Fe and Mn in a method of the direct external standard, reaches 40 %, and at use of a method of the internal standard (an element of comparison Ga) value does not exceed 2,2 %. Experiment within the limits of a casual error (V changes from 2,9 up to 7,4 %) has confirmed theoretical conclusions. 

Cellulose is also commercially modified by acetylation to produce a material suitable for X-ray and cine film. Commercially cellulose ethers are also prepared, such as methylcellulose. This material is water-soluble and gives a highly viscous solution at very low concentrations. Hence it is widely used as a thickener in latex paints and adhesives, in cosmetics and for coating pharmaceutical tablets. 

Fluidized aqueous suspensions of 15% by weight or more of hydroxyethyl-cellulose, hydrophobically modified cellulose ether, hydrophobically modified hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and polyethylene oxide are prepared by adding the polymer to a concentrated sodium formate solution containing xanthan gum as a stabilizer [278]. The xanthan gum is dissolved in water before sodium formate is added. Then the polymer is added to the solution to form a fluid suspension of the polymers. The polymer suspension can serve as an aqueous concentrate for further use. 

Some extended-release preparations are designed with a coating that responds to the acidity of its environment. The polymeric coating of the medicine is formulated for stability during oral delivery and for eventual solubility at the intended organ. The contrasting acidic content of the stomach and the more basic environment of the intestines enable these formulations to function. For example, hydroxypropyl methylcellulose phthalate (HPMCP) (Fig. 14.1.3) is an enteric... 

The physical form of a material destined for oral administration often presents unique challenges. Liquids can be administered as supplied or diluted with an appropriate vehicle, and powders or particulates can often be dissolved or suspended in an appropriate vehicle. However, selection of an appropriate vehicle is often difficult. Water and oil (such as the vegetable oils) are used most commonly. Materials that are not readily soluble in either water or oil can frequently be suspended in a 1% aqueous mixture of methylcellulose. Occasionally, a more concentrated methylcellulose suspension (up to 5%) may be necessary. Materials for which appropriate solutions or suspensions cannot be prepared using one of these three vehicles often present major difficulties. 

While reactions of low-molecular-weight compounds can sometimes be carried out in the gas phase, this technique is not applicable to macromolecular substances since they are not volatile. However, it is indeed possible to let low-molecular reagents act upon solid or dissolved polymers in gaseous form. This is done, for example, in the commercial preparation of methylcellulose by conversion of alkali cellulose with gaseous methyl chloride. 

In this study, the influence of several formulation factors on the release kinetics of potassium chloride from directly compressed matrices is investigated. Formulations containing hydrophilic (methylcellulose, carbomer), plastic (polyvinyl chloride) and wax (glycerol palmitostearate) matrix materials at concentrations of 10%, 15% and 20%, and insoluble excipients, were prepared and tested using the USP XXI-NF XVI rotating paddle method. 

Bulk-forming laxatives are indigestible, hydrophilic colloids that absorb water, forming a bulky, emollient gel that distends the colon and promotes peristalsis. Common preparations include natural plant products (psyllium, methylcellulose) and synthetic fibers (polycarbophil). Bacterial digestion of plant fibers within the colon may lead to increased bloating and flatus. 

Prepare coating solution by adding ethanol and acetone and hydroxyupropyl methylcellulose... 

The values given above pertain to solution on reconstitution of one flavor pack. When dissolved in sufficient water to make 4 L, the final solution contains 125 mEq/L sodium, 10 mEq/L potassium, 20 mEq/L bicarbonate, 80 mEq/L sulfate, 35 mEq/L chloride, and 18 mEq/L polyethylene glycol 3350. The reconstituted solution is isos-motic and has a mild, salty taste. Colyte Flavor Packs are available in citrus berry, lemon lime, cherry, and pineapple. This preparation can be used without the Colyte Flavor Packs and is administered orally or via a nasogastric tube. Each Citrus Berry Flavor Pack (3.22 g) contains hydroxypropyl methylcellulose 2910, citrus berry powder,... 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

The methyl ether of cellulose has a methoxyl content which varies between 6 and 33 %. Methylcellulose can be prepared by the action of methyl chloride or methyl sulfate on cellulose that has been previously treated with alkali. Purification is accomplished by washing the reaction product with hot water. The degree of methylation can be controlled to yield products with varying viscosities. Seven viscosity types of methylcellulose are currently produced with centipoise values ranging from 10 to 4000. Methylated cellulose of low methoxy content is soluble... 

Korshak and his colleagues reported210 that polymerization of tri-O-methyllevoglucosan with boron trifluoride etherate in dichloromethane gives products having the highest reduced viscosity. The yield of polymer increased with temperature, and the reduced viscosity reached a maximum at -20°. In contrast to tri-O-methylcellulose, poly(tri-0-methyl-D-glu-coses) prepared in this way are insoluble in water, acetone, or ether, but are soluble in chloroform and a cresol. These workers concluded that the products are crystalline and unbranched. 

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