Hydroxypropyl-methylcellulose

Paint strippers are also formulated to have high viscosity, otherwise they run off vertical surfaces and thereby fail to penetrate or solubilise the paint to which they have been applied. Hydroxypropyl methylcellulose is the main thickener for paint strippers, which use methylene chloride (dicldoromethane) as the principal component. Hydroxypropyl methylcellulose is useful for this purpose because it is soluble in the orgaiuc component but is not sensitive to the presence of any water that may also be present in the paint stripper. 

Iyer et al. [50] investigated the effects of roto-granulation on the performance of hydroxypropyl methylcellulose (HPMC), gelatin, and poly(-vinylpyrrolidone) (Povidone, PVP). In this process, all three binders produced similar results. However, HPMC was preferred due to prolonged drug release profiles, smaller particle size, and better content uniformity. 

The major commercial viscous vehicles are hydroxypropyl methylcellulose (Isopto ) and polyvinyl alcohol (Liquifilm ). Isopto products most often use 0.5% of the cellulosic and range from 10 to 30 cP in viscosity. Liquifilm products have viscosities of about 4-6 cP and use 1.4% polymer. 

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... 

Figure 14.1.3 The repeating unit of the polymer hydroxypropyl methylcellulose phthalate (HPMCP).

Excipients Cellulose, disodium hydrogen phosphate, hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, mannitol, sodium lauryl sulfate, etc. 

Formuiation The formulation consists of excipients such as carnauba wax, crospovidone, hydroxylpropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, microcrystalline cellulose, and other inactive ingredients. 

Macleod et al. [92] have studied the potential of pectin-chitosan-hydroxypropyl methylcellulose films for colonic drug delivery [92]. The results showed that in all cases the tablets were able to pass through the stomach and small intestine intact. The tablets started to break up once they were in the colon, due to degradation of the coat by colonic bacteria. 

Macleod, G.S., Fell, J.T., Collett, J.H., Sharma, H.L., and Smith, A.M., Selective drug delivery to the colon using pectin chitosan hydroxypropyl methylcellulose film-coated tablets, Int J. Pharm., 187 251-257 (1999). 

Duloxetine hydrochloride, a novel anti-depressive, is known to be acid labile and, consequently, it has been formulated as an enteric-coated tablet. Interestingly, Jansen et al. [97] subsequently found that the drug was destabilised by degradation products within these enteric polymers. The authors found that succinyl and phthalyl residues from the hydroxypropyl methylcellulose acetate succinate (HPMCAS) and hydroxypropyl methylcellulose phthalate (HPMCP) formed... 

Starches Hydroxypropyl methylcellulose (HPMC) Polyvinyl alcohol (PVA)... 

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,... 

Abbreviations. BZC, benzalkonium chloride PS, potassium sorbate CDs, cyclodextrins HP-fS-CD, 2-hydroxypropyl-p-cyclodextrin HPMCAS, hydroxypropyl methylcellulose acetate succinate PEG, polyethylene glycol P-407, poloxamer 407 PVAP, poly vinylacetate phthalate. 

Obara S, Muto H, Shigeno H, et al. A three-month repeated oral administration study of a low viscosity grade of hydroxypropyl methylcellulose in rats. J Toxicol Sci 1999 24(1) 33—43. 

Cappon GD, Fleeman TL, Rocca MS, et al. Embryo/fetal development studies with hydroxypropyl methylcellulose acetate succinate (HPMCAS) in rats and rabbits. Birth Defects Res (Part B) 2003 68 421. 

Hydroxypropyl methylcellulose phthalate (HPMCP) dissolves at pH greater than 5 and has two major grades, HP-55 and HP-55S. HPMCP shares the same problem as CAP and needs shellac to prevent permeation of water vapor and gastric fluids. 

Hydroxypropyl methylcellulose acetate succinate (HPMCAS) dissolves at pH higher than 5, and there are three kinds of HPMCAS—AS-LG, AS-MG, and AS-HG. Triethyl citrate is a common plasticizer used with HPMCAS. 

Hydroxpropyl Cellulose Hydroxypropyl Methylcellulose Isobutylene-Isoprene Copolymer Locust Bean Gum... 

Figure 2 illustrates the temperature dependence of the swelling degree as a function of precursor polymer type. Methylcellulose (MC), hydroxypropyl-methylcellulose, type E (HPMC-E) and hydroxypropylmethylcellulose, type K (HPMC-K) gels have comparable effective crosslink densities of about 2 x 10 5 mol/cm3 (as determined from uniaxial compression testing), while the crosslink density of the hydroxypropylcellulose (HPC) gel is about half this [52]. The transition temperature for each gel is within several degrees of the precursor polymer lower critical solution temperature (LCST), except for the MC gel, which has a transition temperature 9 °C higher than the LCST. The sharpness of the transition was about 3%/°C, except for the HPC gel transition, which was much sharper - about 8%/°C. 

Hydroxypropyl methylcellulose Coating agent Titanium dioxide Opacifier... 

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