HPMC film

Oxygen permeability related to the looseness of film section but water vapor permeated more rapidly through gelatin film, which is tighter than HPMC film. Water vapor is considered not to permeate directly through the films and the permeability may relate to the water content of the films. 

Q = 240 m/t a, Q rate of water vapor permeability, m increased weight of CaCb (mg), t time (hr), a effective area of films (cm ) 

---

Figure 3. Positive ion SSIMS spectrum of HPMC film.

Careful characterization of moisture interactions in cellulose derivatives has been reported for HPMC films, both unplasticized and plasticized. Using various techniques (a radiotracer technique involving the use of tritiated water, DSC and TGA), some authors [73] proposed the classification of the water present into three categories the tightly bound water present in plain HPMC films was located in the ordered regions of the polymer and was absent in plasticized films. The moderately bound water (detectable by TGA) was in the rank order of the hydrophilicity of the polymer additives and this order was reversed for the calculated free water content. 

FIGURE 11.7 (a) Peak force (adhesive strength) and (b) work of adhesion of HPC and HPC HPMC films measured using Texture Analyzer and rabbit intestinal mucosa as a substrate (n = 5). (Reprinted with permission from Repka, M.A. et al., Eur. J. Pharm. Biopharm., 59, 189, 2005.)... 

Hydroxypropylmethylcellulose HPMC Cold water, GI fluids, methanol/methylene chloride, alcohol/fluorohydrocarbons Excellent film former and readily soluble throughout GIT low-viscosity grades to be preferred, e.g., Methocel HG (Dow)... 

Macleod, G.S., Collett, J.H., Fell, J.T. (1999). The potential use of mixed films of pectin, chitosan and HPMC for bimodal drug release. Journal of Controlled Release, 58, 303-310. 

Hydroxy propyl methyl cellulose (HPMC).35 HPMC is a partly O-methylated and 0-(2-hydroxypropylated) cellulose available in several grades that vary in viscosity and extent of substitution. It is used widely in pharmaceutical formulations, especially in oral products, as a tablet binder, in film coating, and as controlled release matrix. Soluble in cold water, it forms a viscous colloidal solution. For a 2% aqueous solution (20°C), viscosity can range from 2.4 to 120,000 mPa-s. High-viscosity grades can be used to retard the release of water-soluble drugs from a matrix. 

The polymers are usually applied either from aqueous or from organic solvent. More recently, aqueous dispersions or redispersible powders of the polymers have become available that ensure economical, fast, and environmentally safe processing of the film coatings. In some cases it might be necessary to prevent an interaction between the acidic functional groups and the drug. In these cases a subcoat (e.g., of hydroxypropylmethylcellulose [HPMC]) is recommended. 

Figure 14.3 Chromatograms of excipients in film-former class under different mobile phase pH. In both plots, the curves from the bottom are blank, HPMC, acacia, sucrose NF, HPC, povidone and Eudragit EPO, respectively. The sample solvent, mobile phase and column used are (a) 20% ACN-80% pH 2, 25 mM phosphate buffer, a gradient from 30% ACN-70% pH 2, 25 mM phosphate buffer to 80% ACN-20% pH 2, 25 mM phosphate buffer and a Zorbax SB-C8, 4.6 x 150 mm, 3.5 p.m column at 35°C, respectively and (b) 20% ACN-80% pH 7, 25 mM phosphate buffer, a gradient from 30% ACN-70% pH 7, 25 mM phosphate buffer to 80% ACN-20% pH 7, 25 mM phosphate buffer and a Zorbax XDB-Cg, 4.6 x 150 mm, 3.5 p,m column at 35°C, respectively. In both cases, samples were injected at 1800 p,L, the flow rate of mobile phase was 1 mL/min and the detection was at 210 nm. An on-bench examination of the mixture of either 80% ACN-20% pH 2, 25 mM phosphate buffer or 80% ACN-20% pH 7, 25 mM phosphate buffer revealed no precipitation, so they were suitable as the mobile phase.

HPC (Klucel E5, Hercules hydroxypropyl molar substitution, MS-3) and HPMC (Methocel E15, Colorcon hydroxypropyl molar subsitution, MS-0.23s degree of methoxyl substitution DS-1.88) were studied as a thin film of approximate thickness of 5-10 urn cast from an aqueous solution onto a clean aluminium substrate and allowing the solvent to evaporate. Scanning electron microscopy of films prepared in this manner revealed a continuous surface free from cracks and aberrations. 

These findings afford a clear and unequivocal analysis of the HPC and HPMC polymeric films. The elucidation of the surface... 

Table 6 gives commonly used polymers for film coating of core tablet. With the exception of HPMC, the polymers are rarely used alone but are combined with other polymers to optimize the film-forming properties. A polymer for film coating will ideally meet the following criteria ... 

Soluble in water and GI fluids has similar film-forming properties to HPMC but is less soluble in organic solvents, which limited its popularity when solvent... 

Most coating compositions are based on hypromellose (HPMC) as film-forming polymer and contains microcrystalline cellulose (MCC) (see Table 17). 

FIGURE 31 (a) Tablet coated with HPMC smooth film, medium discontinuity between film and core. (b) Tablet coated with SEPIFILM 752 white clear edge perfectly coated, good adhesion of film to core and continuity between film and core. 

Substituted Cellulose Ethers. Since their introduction for ophthalmic use, MC and other substituted cellulose ethers such as hydroxyethylcellulose, hydroxypropylcel-lulose, hydroxypropyl methylcellulose (HPMC), and carboxymethylcellulose (CMC) have been used in artificial tear formulations.These colloids dissolve in water to produce colorless solutions of varying viscosity. They have the proper optical clarity, a refractive index similar to the cornea, and are nearly inert chemically. Their relative lack of toxicity, their viscous properties, and their beneficial effects on tear film stability have made cellulose ethers useful components of artificial tear preparations. Historically, the most frequently used representative of this group was MC. 

---