Pseudolatexes

J. Plaizier-Vercammen, G. Suenens, Evaluation of Aquateric, a pseudolatex of cellulose acetate phthalate, for its enteric coating properties on tablets STP Pharma Sci 5 307-312 (1991). 

Another early attempt to formulate a nanoparticulate system for the delivery of pilocarpine was made by Gurny [99], This formulation was based on pilocarpine dispersed in a hydrogen CAP pseudolatex formulation. Gurny and co-workers [101] compared the formed nanoparticles to a 0.125% solution of hyaluronic acid some years after their first investigation and found that the viscous hyaluronic acid system showed a significantly longer retention time in front of the eye than the pseudolatex formulation. 

Khan, M. A., Sastry, S. V., Vaithiyalingam, S. R., Agarwal, V., Nazzal, S., and Reddy, I. K. (2000), Captopril gastrointestinal therapeutic system coated with cellulose acetate pseudolatex Evaluation of main effects of several formulation variables, Int. J. Pharm., 193, 147-156. 

Quintanar-Guerrero, D. Alleman, E. Fessi, H. Doelker, E. Pseudolatex preparation using a novel emulsion-diffusion process involving direct displacement of partially water-miscible solvents by distillation. Int. J. Pharm. 1999, 188, 155-164. 

Bodmeier, R. Paeratakul, O. The effect of curing on drug release and morphological properties of ethylcellulose pseudolatex-coated beads. Drug Dev. Ind. Pharm. 1994, 20 (9), 1517-1533. 

Hutchings, D. Clarson, S. Sakr, A. Studies of the mechanical properties of free films prepared using an ethylcellul-ose pseudolatex coating system. Int. J. Pharm. 1994,... 

Surelease Colorcon Water Insoluble Ethylcellulose pseudolatex... 

Eudragit RS30D Rohm Water Insoluble 1 2 0.1 Poly(EA/MMA/TAMCl) pseudolatex... 

Bodmeier, R. Chen, H. Hydrolysis of cellulose acetate butyrate pseudolatexes prepared by a solvent evaporation—microfluidization method. Drug Dev. Ind. Pharm. 1993, 19 (5), 521-530. 

Examples of aqueous coating solutions include water-soluble low molecular weight cellulose ethers, emulsion polymerization latexes of polymethacrylates, and dispersions of water-insoluble polymers such as ethyl-cellulose in the form of pseudolatex. These solvent-free coating solutions provide a range of different coatings... 

Fig. 26 Differences observed in the mechanism of film formation from latex and pseudolatex dispersions and from micronized coating materials.

Chang RK, Iturrioz G, Luo CW. Preparation and evaluation of shellac pseudolatex as an aqueous enteric coating system for pellets. Int Pharm 1990 60 171-173. 

The movement of the pharmaceutical industry away from volatile solvents for coating applications coupled with advancements in coating equipment design led to an increase in the popularity of latex and pseudolatex coating systems. Latexes and pseudolatexes are both colloidal dispersions of polymer droplets in a continuous aqueous phase, the difference between them being that latex systems are formed by emulsion polymerization... 

Aquacoat ECD and Surelease are two commercially available ethylcellulose pseudolatex dispersions. Aquacoat ECD. a product of FMC Corporation, is produced by an emulsification/solvent evaporation proce.ss that utilizes sodium lauryl sulfate and cetyl alcohol as colloid. stabilizers (64). The Aquacoat ECD dispersion contains approximately 27% ethylcellulose and 30% total solids. The dispersion does not contain plasticizer, and therefore an appropriate plasticizer must be added to the dispersion prior to coating. The dispersion is typically diluted to a final solids content in the range of 15-20% prior to spray coating. Although, intended to be a pH-independent sustained release coating system, the content of sodium lauryl sulfate in the Aquacoat ECD dispersion has been demonstrated to cause reduced drug release rates in acidic media versus media of neutral pH (65.66). 

Surelease. a product of Colorcon. is produced by first melt extruding ethylcellulose with oleic acid and dibutyl sebacate (DBS) (or fractionated coconut oil) to form a molten plasticized polymeric blend. This molten blend of plasticized ethylcellulose is then introduced into an ammoniated water solution under high shear and pressure to disperse small droplets of plasticized ethylcellulose into the water phase (67). Ammonium oleate is produced in situ during this emulsification process to stabilize the colloidal ethylcellulose particles (67). Additional purified water is then added to reduce the final solids content of the pseudolatex dispersion to 25%. The Surelease coating system does not contain an ionic surfactant, and therefore does not exhibit the pH-dependent drug relea.se observed with Aquacoat ECD (66),... 

The Tg of bulk ethylcellulose is in the range of 129-133 C, and therefore at ambient conditions films of ethylcellulose are substantially brittle. To be used in film coating applications, ethylcellulose requires the addition of pla.sticizer to improve film flexibility and toughness. The Tg of dried latex particles of Aquacoat ECD has been reported to be 89 C (7). The reduced Tg of ethylcellulose particles dried from a pseudolatex is the result of the temporary plasticizing effects of water. Although the Tg of ethylcellulose... 

Bodmeier R. Paeraiakul 0. Process and formulation variables affecting the drug release from chlorpheniramine malcate-loaded beads coated with commercial and self-prepared aqueous ethyl cellulose pseudolatexes. Int J Pharm 1991 70( l-2) 59-68. 

Bodmeier R, Guo X, Pacratakul O. Process and formulational factors affecting the drug release from pellets coated with the ethylcellulose-pseudolatex aquacoat. In McGinity JW, ed. Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms. 2nd ed. New York Marcel Dekkcr, Inc., 1997 55-80. 

EC is soluble in many organic solvents and insoluble in water, so the polymer can be applied to the substrate from (1) an organic solution, typically using a low MW alcohol, acetone, or a mixture thereof or (2) an aqueous pseudolatex dispersion. The term pseudolatex is used because the dispersed nanoparticles in an aqueous latex are considered to be produced from a polymerization reaction. Aqueous EC pseudolatexes, however, are produced utilizing either melt-processing... 

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