Polymers hydroxypropyl methylcellulose

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

Jansen PJ, Oren PL, Kemp CA, Maple SR, Baertschi SW. Characterization of impurities formed by interaction of duloxetine HC1 with enteric polymers hydroxypropyl methylcellulose acetate succinate (HPMCAS) and hydroxypro-pyl methylcellulose phthalate (HPMCP). J Pharm Sci 1998 87(1) 81—85. 

Another example of an amine reacting with a formulation component is found in the case of duloxetine hydrochloride (84). This example, which is also discussed in Chapter 2, is summarized in Figures 49 and 50. In this example, the secondary amine of duloxetine hydrochloride reacted with the enteric coating polymer hydroxypropyl methylcellulose acetate succinate (HPMCAS) to form a succinamide degradation product. This reaction occurred under both stress conditions (60°C for 14 days) and during formal stability studies (30°C/60% relative humidity and 40°C/75% relative... 

Torsion braid analysis is particularly useful in the evaluation of plasticizers. Soft materials each containing different plasticizers or different amounts of a plasticizer can be compared. For example, the film-forming polymer (hydroxypropyl)methylcellulose plasticized with poly(ethylene glycol) 200... 

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. 

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... 

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. 

For hydroxypropyl methylcellulose acetate succinate, a novel enteric dry coating method has been developed [31]. The unique feature of this method is that the enteric polymer is added in powder form (e.g., mixed with talcum directly to tablets or pellets) whereas a plasticizer diluted with paraffin is sprayed separately. The tablet core temperature is around 40°C, and the film is cured for a short time. To achieve a homogenous film, the rates of powder feeding and plasticizer spray have to be adjusted such that the two processes start and end simultaneously. 

Sarkar, N. (1979). Thermal gelation properties of methyl and hydroxypropyl methylcellulose. /. Appl. Polym. Sci. 24 1073-1087. 

Water-soluble hydroxypropylmethyl cellulose and water-insoluble cellulose acetate are further treated with phthalic anhydride or succinic anhydride to yield hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate, and hydroxypropyl-methylcellulose acetate succinate. These polymers are used as enteric materials and are water soluble or insoluble above or below a specific pH, respectively. 

A popular approach to improve ocular drag bioavailability is to incorporate soluble polymers into an aqueous solution to extend the drug residence time in the cul-de-sac. It is reasoned that the solution viscosity would be increased and hence solution drainage would be reduced. The more commonly used viscolyzing agents include PVA and derivatives of cellulose. Cellulosic polymers, such as methylcellulose, hydroxyethylcellulose (HEC), hydroxypropyl-methylcellulose (HPMC) and hydroxypropylcellulose (HPC), are widely used as viscolyzers showing Newtonian properties. They have common properties ... 

Generally, the barrier or rate-controlling films are more permeable to water than the carrier films. The materials used for this purpose consisted of a base, film forming water-soluble polymer in combination with at least one hydrophilic component such as hydroxypropyl methylcellulose or polyvinylpyrrolidone. The polymers used were the same as those for the carrier films. Some recent developments are discussed herein. 

A review of vaginal bioadhesive formulations indicates that bioadhesive tablets have been used for localized treatment of diseases in the vaginal tissue.F ° l For example. Bleomycin, an antitumor agent, was incorporated into a flat-faced disk fabricated from a combination of hydroxypropyl cellulose and poly-(acrylic acid) (Carbopol 934). ° The tablet was designed to release Bleomycin at a slow rate to minimize irritation to healthy mucosa. Another vaginal tablet is formulated from the combination of poly(acrylic acid) with hydroxypropyl methylcellulose and ethylcellu-lose. Other polymer combinations evaluated for potential bioadhesive vaginal delivery include poly(acrylic acid) and sodium carboxymethyl cellulose with Avicel PH102 (methylcellulose) as the diluent. Insulin has been formulated in a cross-linked poly(acrylic acid) gel... 

Among the polymers used in lens comfort solutions are polyvinyl alcohol, polyvinylpyrrolidone, dextran, and various cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methylcellulose. Surfactants include certain poloxamer and poloxamine compounds. Other normal components comprise appropriate preservative(s) as well as buffering and tonicity-adjusting agents. 

Fig. 27 Infiuence of the type of polymer application on film properties (top and side view). HP55 (HPMCP)-coated pellet, prepared from a micronized film dispersion (A). HP55 [hydroxypropyl methylcellulose (HPMCP)]-coated pellet, prepared from an organic solution (B).

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