Application of solid dispersions with enteric coating agents to overcome some pharmaceutical problems.

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Abstract
A solid dispersion technique with enteric coating agents was applied to two drugs which present some pharmaceutical problems. The first drug, digoxin, is poorly water-soluble and chemically unstable in an acidic medium. The solid dispersions suppressed the dissolution rate of the drug in JP X 1st fluid (JP dinsintegration medium, pH 1.2), and improved the chemical stability. In JPX 2nd fluid (JP disintegration medium, pH 6.8), the solid dispersion showed rapid dissolution and supersaturation. It was concluded that this technique can provide an effective dosage form of digoxin for gastrointestinal absorption. The second drug, dipyridamole, is a poorly water-soluble organic base. The solid dispersion technique was applied to prepare a delayed absorption dosage form with good bioavailability. The solid dispersions showed suppressed a dissolution in an acidic medium, and gave supersaturation in a neutral or a alkaline medium. Oral administration of this dosage form resulted in delayed absorption with good bioavailability.