Figure 3: Comparative taste panel results with quinine hydrochloride tablets.
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A robust film-coating formulation is needed in the compression of coated particles into tablets as with taste-masking of pediatric,
chewable acetaminophen tablets. Maintaining coating integrity and eliminating particle-coating failure are important for intact
coating functionality after compression. To determine optimal use level for similar applications with methyl methacrylate
and diethylaminoethyl methacrylate copolymer dispersions, cast films were plasticized with tributyl citrate, triethyl citrate,
and acetyltriethyl citrate at levels between 10 and 25% for elongation at break comparison. Elongation at break values of
approximately 100% were attained using 13–15% plasticizer content range, which provides sufficient flexibility for coated
particle compression applications (3).
Figure 4: Acetaminophen release at pH 1.2.
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Acetaminophen crystals, with a mean particle size of 300 µm, were coated using a methyl methacrylate and diethylaminoethyl
methacrylate copolymer (6:4) coating consisting of 8% talc, 0.4% colorant, 1.51% triethyl citrate (15% relative to polymer
content), 33.33% copolymer, and 56.67% water (20% solids content). Coated samples were taken at 7.5, 15, 22.5, and 30% weight
gain. A coating weight gain of 7.5% (w/w) provided significant taste-masking with immediate dissolution at pH 1.2 (see Figure
4).
Figure 5: Impact of talc on vapor permeability.
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With regard to moisture protection, the use of a lipophilic plasticizer and pigments can optimize the protective properties
of a methyl methacrylate and diethylaminoethyl methacrylate copolymer film coating. Vapor permeability studies performed on
sprayed films containing 15% triethyl citrate (w/w based on polymer) and increasing levels of talc (0–40%) reveal a decreasing
level of moisture permeability with increasing talc content (see Figure 5).
Figure 6: Moisture uptake of sorbitol tablets at 30 °C and 70% relative humidity.
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As an example, sorbitol, with its highly hygroscopic properties, was compressed into tablet cores containing 49.75% sorbitol
(Neosorb P 60 W, Roquette), 49.75% Ludipress (BASF), and 0.5% magnesium stearate to a hardness of 110 N. The tablets were
coated with a 34.66% methyl methacrylate and diethylaminoethyl methacrylate copolymer film also containing 1.35% tributyl
citrate (13% relative to polymer), 0.26% butylated hydroxytoluene (2.5% relative to polymer), 8.00% talc, and 55.73% water
(20% solids content total). Sample tablets taken at coating levels of 0, 3, 4.5, 6, 9, 12, and 20 mg/cm2 and placed on 30 °C and 70% stability showed an increase in moisture-barrier properties with an increase in coating weight
gain (see Figure 6).
Based on the physicochemical properties of methyl methacrylate and diethylaminoethyl methacrylate copolymer dispersion, optimized
protective film coatings can be formulated to provide taste-masking and moisture-barrier properties for bitter and moisture-sensitive
active ingredients.
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