Step 1: Understanding the Concept.
Different Eudragit grades are chosen for coating tablets based entirely on the release profile the formulator wants, fast, delayed, or extended.
Step 2: Key Approach.
Recall that Eudragit NE40D is classified as a neutral, water-insoluble but permeable polymer, then match that property to the tablet type that needs a slow, steady drug release.
Step 3: Detailed Explanation.
Because Eudragit NE40D does not dissolve in water, it cannot be used where fast disintegration is required, which rules out sublingual and IR tablets that depend on rapid breakup or dissolution.
Its permeability allows drug molecules to slowly diffuse through the coated film over hours, which is the working principle behind controlled-release tablet technology.
Buccal tablets instead need the coating or matrix to stick to the cheek lining, a property that comes from mucoadhesive polymers, not from Eudragit NE40D's insoluble film.
Step 4: Final Answer.
Coating tablets with Eudragit NE40D is done to prepare CR tablets.