Swellable coatings

Thick coating consisting of water-insoluble, non-swellable polymers... 

Swellable hydrogels, (IV), used for sensor coatings were prepared by Van Antwerp [4] and were capable of water uptake of at least 200% by weight. 

Gazzaniga A, Sangalli ME, Conte U, CarameUa C, Colombo P, and La Manna A. On the release mechanism from coated swellable minimatrices. Int. J. Pharm. 1993 91 167-171. 

Soluble cap Coated, swellable plug Capsule content (drug, excipient)... 

Fig. 9 Capsular-shaped pulsatile drug delivery system, consisting of an impermeable capsule body and (A) a swellable, insoluble coated plug and (B) an erodible plug. (From Ref. l)...

Materials used to coat pharmaceutical products are primarily based on acrylic and cellulosic polymers and the aqueous solubility characteristics of these compounds generally dictate their uses. Sustained release coatings are water-insoluble or swellable films through which the medicament slowly diffuses. Drug products coated with these polymers are administered less frequently and the high peak plasma concentrations... 

Coppi G, lannuccelli V, Cameroni R. Polysaccharide film-coating for freely swellable hydrogels. Pharm Dev Tech 1998 3(3) 347— 353. 

The core may be a water-soluble polymer, an inert salt or, as in the case of metoprolol fumarate, the drug itself, whose saturated solution has an osmotic pressure of 32.5 atm. The osmotic tablet of nifedipine is described in detail in Fig. 8.38, which shows the semipermeable cellulose acetate coating, the swellable hydrogel layer of polyoxyethylene glycol and hydroxypropylmethylcellulose (HPMC) and the dmg chamber containing nifedipine in HPMC and PEG. 

Enteric targeting may also include other, new dosage forms, which remain located in the stomach and start releasing their dmg from there. These gastric-retention systems consist of a swellable core, usually film coated with highly flexible polymers that disintegrate after a certain time of floating in the stomach. Deshpande et al. [71] have described such a system recently. 

Biomedical applications. In a review, Carville [4] enumerated many biomedical applications of LPG-sensing platforms that make use of specific affinity coatings or swellable polymers permitting selective, quantitative changes in the refractive index when target analytes are present. 

The industrial problems limiting earlier industrial thickeners in the coatings area were overcome with HEUR thickeners. With increasing sales, production limitations were addressed and the batch processes were replaced with semicontinuous techniques. Hydrophobe modification of industry standards (hydroxyethylcellulose and alkali-swellable emulsions) produced by proven industrial processes entered the market and broadened the technology. 

X HE RELATIVE COST OF MANUFACTURING hydrophobically modified, water-soluble polymers is the primary determinant in their market acceptance. The lowest-cost associative thickeners used in coating formulations are hydrophobically modified, alkali-swellable emulsions (HASE). The extensive history leading to the development of this technology is reviewed in the preceding chapter their utilization and limitations are discussed in Chapters 27 and 28. 

Catellani, R.L. Colombo, R Reppas, N.A. Santi, R Bettini, R. Rartial permselective coating adds an osmotic contribution to drug release from swellable matrixes. J. Pharm. Sci. 1998, 87 (6), 726-731. Lim, S. Manufacture of oral dosage forms delivering both immediate-release and sustained-release drugs. US Ratent 0795324 0598309 1330839 WOOO/23045. 6682759. January 27, 2004. 

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