The key factor in roll compaction is that the binding of particles results solely from the compaction forces requiring a certain degree of compactibility of the powder blend. Some active ingredients can be compressed directly, whilst others require the addition of excipients, which are selected based on their compaction properties. Consequently, in RC, the material to be compacted often consists of a mixture of (poorly compactible) drug substance and (compactible) excipients in order to obtain a ribbon with sufficient mechanical strength so as to result in a sufficiently coarse flowable granulate. Commonly used excipients for this process are microcrystalline cellulose, dicalcium phosphate, lactose monohydrate and mannitol.