What is the most common method for tableting active ingredients that are chemically incompatible?

• A. Microencapsulation
• B. Film coating
• C. Use of stabilizers
• D. Use double layer tableting

Answer: (D)

When two active ingredients are chemically incompatible, the most practical solution is to use a bilayer tablet—two distinct layers pressed together so each drug remains physically separated within the same dosage form. This setup prevents direct interaction between the actives during manufacturing, storage, and in the gastrointestinal environment, while still allowing precise dosing of both drugs. Each layer can have its own excipients and disintegration/release characteristics tailored to the specific drug, providing stability and controlled performance.

Other methods aim at protection or stabilization, but they don’t inherently keep two incompatible actives apart in the final tablet. Microencapsulation is great for isolating a single component or masking taste, but coordinating two incompatible drugs through separate microcapsules in one tablet adds complexity. Film coating protects the tablet surface or masks taste but doesn’t separate the two actives inside. Stabilizers help with the stability of a single drug but don’t prevent interaction between two different drugs within the same dosage form.