| 摘要 |
Film coatings for enteric and colonic release at selected pH are provided by selecting and/or formulating a shellac of a predetermined acid number. The method includes the selection of the acid number to provide the release at the specified pH and a method of providing a shellac of a predetermined acid number by blending of shellacs of different acid numbers. In general, films that release or dissolve at or above pH 7.4 are based on the selection of shellac with an acid number below 74. Films that release or dissolve above pH 7.0 are comprised of shellac selected with an acid number below 80. Films that release or dissolve at below pH 7.0 are comprised of shellac selected to have an acid number above 80. The film coating may be modified with a water soluble resin and/or a plasticizer. Preferably the shellac will comprise 50% or more of the resin system, and is formed out of water, not alcohol.
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