Drug Release from Coated Dosage Forms

Changes in Drug Release from Coated Dosage Forms 

The stability of the drug release characteristics of film-coated tablets and pellets is affected by the stability of the films. This should be the case especially when the film contributes significantly to the rate-limiting step in the release. The stability of a film coat 

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Since the development of the Spansule brand (Smith Kline Beech am) of coated beads and granules in the late 1960s, various dmg product technologies have been developed and patented to achieve extended durations of therapeutic effects. Each of these does so by various mechanisms of control of dmg release from adrninistered dosage forms. Each method has its advantages and disadvantages, a discussion of which is available in the pharmaceutical hterature (see Drug delivery systems) (21). 

Hypromellose or hydroxypropylmethylcellulose is a partly O-methylated and 0-(2-hydroxypropylated) cellulose [25]. It is used from 10% up to 80% w/w for controlled drug release in solid dosage form and from 2% to 20% w/w as coating solution for tablets and pellets [25,30,31 ]. Hydroxypropylmethylcellulose is a nonionic polymer with pH of a 2% w/w aqueous solution ranging from 5 to 8. It is soluble in water. Being nonionic, it will not form complexes with metallic salts or ionic compounds that can possibly lead to the precipitation of insoluble compounds [32]. Hydroxypropylmethylcellulose matrix hydrates and swells into a gel layer in the direction of matrix surfaces to core when it is contacted with the dissolution medium [14,20,33]. Erosion of gel takes place thereafter and may occur simultaneously with the subsequent phases of matrix hydration and swelling [14]. The swelling and erosion properties of a solid matrix made of... 

J. M. Conrad, and J. R. Robinson. Sustained drug release from tablets and particles through coating, in H. A. Lieberman and L. Lachman (eds.), Pharmaceutical Dosage Forms Tablets, Vol. 3. New York Marcel Dekker, 1982, pp. 149-221. 

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. 

Siepmann, R, Hoffmann, A., Leclercq, B., Carlin, B., Siepmann, J. How to adjust desired drug release patterns from ethylcellulose-coated dosage forms. J. Control. Release 2007, 119(2), 182-189. 

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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