HPMCP

The most commonly used polymers are cellulose acetate phthalate [9004-38-0] (CAP), poly(vinyl acetate phthalate) [34481-48-6] (PVAP), hydroxypropylmethyl-ceUulosephthalate [71138-97-1] (HPMCP), and polymethacrylates (111) (see Cellulose esters). Acrylate copolymers are also available (112). Eigure 11 shows the dissolution behavior of some commercially available enteric materials. Some manufacturers supply grades designed to dissolve at specific pH values with increments as small as 0.5 pH unit (113). 

Fig. 11. Dissolution as a function of pH of various enteric polymers. (—) represents HPMCP (HP-50) (-), HPMCP (HP-55) (—), PVAP ( ), CAP.

Hydroxypropylmethyl cellulose phthalate (HPMCP) Poly(methacrylates)... 

Hydroxypropylmethylcellulose phthalate HPMCP As above, if pH >4.5 Dissolves in proximal end of duodenum... 

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).

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... 

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. 

Abbreviations. PEG, polyethylene glycol HPMCP, hydroxypropylmethylcellulose phthalate Y, Yes. 

FIGURE 18.10 Inhibitory effect of polymers on recrystallization of nifedipine (NP) from a supersaturated solution at pH 6.8. HPMCAS, hydroxypropylmethyl cellulose acetate succinate HPMC, hydroxypropylmethyl cellulose HPMCP, hydroxypropylmethyl pthate PVP, polyvinyl pyrrolidone MAEA, methacrylic acid ethyl acrylate copolymer. (From Tanno, F., Y. Nishiyama, H. Kokubo, S. Obara. ZWMjDev Ind Pharm30 13. 

Figure 11 Structures of enteric polymers HPMCAS and HPMCP.

Figure 12 Structures of duloxetine succinamide and duloxetine phthalamide, the major impurities resulting from interaction between duloxetine and the enteric coatings HPMCAS and HPMCP during stress testing or long-term stability studies.

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. 

CAP aqueous CAP organic HPMCP aqueous HPMCF organic... 

The salt form of the polymer may also play a role in determining the performance of the formulation. Kane et al. [32] found that cellulose acetate phthalate was more effective than cellulose acetate trimellitate in controlling the dissolution of sulfothiazole-sodium tablets with cellulose acetate. The enteric properties of hydroxypropylmethylcellulose phthalate (HPMCP) were found to depend on the solubility of the drug that was coated. 

As previously discussed, food effects are an important parameter for enteric-coated systems, especially for drugs, that are sensitive to food. Pancreatic enzyme-containing products fail when they come in contact too early with lipids, proteins, and carbohydrates present in food. The clinical efficacy of pancreatic enzymes formulated as enteric-coated tablets was investigated in man and dog [44], The enteric materials examined were hydroxypropyl methylcellulose phthal-ate (HPMCP), cellulose acetate phthalate (CAP), and the methacrylic acid copolymer USP/NF Type C. In vivo behavior monitored by x-ray scintigraphy showed clear differences between the three coating formulations. HPMCP-coated products adhered to the gastric mucosa, whereas CAP and methacrylate copolymer... 

The experimental data on the rate constants for formation of La(III)-HPMBP and La(III)-HPMCP are given in Table 7.21 and the reaction scheme is given below. 

Fig. 7.28. Plot of log / ll and log Afj vs atomic number of lanthanides for HPMBP and HPMCP [83].

Kim, I. H., Park, J. H., Cheong, I. W., and Kim, J. H. (2003), Swelling and drag release behavior of tablets coated with aqueous hydroxypropyl methylcellulose phthalate (HPMCP) nanoparticles, /. Controlled Release, 89,225-233. 

HPMCP Shin-Etsu Water-ethanol Intestine Hydroxypropylmethylcellulose phthalate... 

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).

Cellulose phthalate hydroxypropyl methyl ether HPMCP hydroxypropyl methylcellulose benzene-1,2-dicar boxy late 2-hydroxypropyl methylcellulose phthalate methylhydroxypro-pylcellulose phthalate. 

Ito R, Toida S. Studies on the teratogenicity of a new enteric coating material, hydroxypropyl methylcellulose phthalate (HPMCP) in rats and mice. Med Soc Toho-XJniv 1972 19(5) 453 61. 

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