Exploring Excipient Functionality - Pharmaceutical Technology

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PharmTech Europe

Exploring Excipient Functionality
This technical forum is part of a special issue on Solid Dosage and Excipients.

Pharmaceutical Technology
Volume 35, pp. s6-s11

Figure 3: Comparative taste panel results with quinine hydrochloride tablets.
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.
Acetaminophen crystals, with a mean particle size of 300 m, 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.
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.
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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