Methyl cellulose water absorption

Fig. 9. Correlation plots of (the time corresponding to the inflection point on the differential two-stage curve) and Ct° (the initial concentration of each differential absorption) O PMMA-methyl acetate (30° C). APSt-benzene (25° C). IPSt-LC-benzene (35° C). IPSt-HC-benzene (35° C). cellulose acetate-methyl acetate (20° C). g cellulose nitrate-acetone (25° C). A regenerated cellulose-water (15° C). PMMA = polymethyl methacrylate. APSt = atactic polystyrene. IPSt-LC = isotactic polystyrene of low crystallinity. IPSt-HC = isotactic polystyrene of high crystallinity. Taken from Fujita, Kishimoto and Odani...

If the drug is insoluble in water, suspensions have to be administered. In such cases vehicles like sesame oil, hydroxy-methyl-cellulose or hydroxy-ethyl-cellulose can be used. The selection of the vehicle is a critical issue because of inherent toxicity of the vehicle used frequently for kinetic and metabolism studies (e.g. vehicles which form metabolically oxalic acid). Natural oils such as sesame or com oil can be used. However, it should be checked whether the use of oily vehicles alters the gastrointestinal absorption due to their laxative properties and whether oily vehicles can cause oil granulomas (reaction to oily vehicles in the reticulo-endothelial system) in case of parenteral administration. 

As shown in Table 6.1, the water absorption of methyl cellulose-modified systems increases with rising polymer-cement ratio. By contrast, the water permeation decreases with an increase in the polymer-cement ratio, as represented in Fig. 6.2.f l Methyl cellulose causes a considerable swelling due to water absorption, and seals capillary cavities in the modified systems, and hence decreases permeability. 

In an in vitro percutaneous study performed on rodent and pig skin with DEBT (diethyl-m-toluamide CAS no. 134-62-3), permethrin and carbaryl results were that no permethrin was absorbed. It was believed by the authors that DEBT inhibited the absorption of permethrin (Baynes et al. 1997). Bast et al. (1997) studied the percutaneous absorption of permethrin through the isolated perfused rabbit ear. Permethrin was applied in isopropyl myristate (reference ointment) or in ethanol. The ethanol was evaporated off skin, and the skin was covered with 1.5 (w/w) methyl cellulose in water. The authors measured the appearance rates (pmol min cm ) of 3-phenoxy benzene methanol (CAS no. 13826-35-2) and 3-phenoxybenzoic acid (CAS no. 3739-38-6) in the effusate after dermal application (3.61 pmol cm of skin). No permethrin per se was found in the effusate. The metabolites were believed to be from impurities in the permethrin. From the concentration that permethrin constitutes in a pharmaceutical brand (Ambush ) and from detection limits. Bast et al. (1997) calculated a Kp of 2.63 x 10 cm h . ... 

Methyl cellulose M - RsH or Cl Insoluble in hot water and soluble in cold water and organic solvents. The solubilization of MC in organic solvents depends of the degree of substitution. No good moisture barriers. Excellent barrier against migration of fats and oils. It can be used to reduce oil absorption in fried products. 

Dicyclohexyl phthalate (DCHP) n. C6H4 (COOC6Hii)2. a plasticizer for PVC and many other resins. It imparts good electrical properties, low volatility, low water and oil absorption, and resistance to extraction by hexane and gasoline. In vinyls DCHP is usually combined with other plasticizers. In cellulose nitrate, polystyrene, poly-methyl methacrylate, and ethyl cellulose it serves as a primary plasticizer. 

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