Granulation and Drying: The Choice of Excipients Matters

Solid dosage forms such as granules, tablets, capsules and sachets may not be as appealing as some of the novel drug delivery forms of recent years, but they will remain far and away the most prevalent dosage form on the market. They consist of a mixture of active pharmaceutical ingredients (API) and excipients. The excipient type or the excipients combination can impact important properties of the final powder like flowability, compactability, and compressibility, which may change attributes of final dosage forms (content uniformity, dissolution rate in the body). The optimization of mentioned properties strictly depends on intermediate process steps like granulation where small particles gather to form particle enlargement by agglomeration. In this way, granules are produced that flow and compress better than starting materials.
Granulation processes can be divided into two types: wet and dry granulation. The first requires water or a binding solution (water and binding agents), where the water is consecutively removed by drying (e.g., fluidized bed dryer). Dry granulation is performed by mechanical compression or compaction and does not require liquid.
In this application report, different relative humidity, temperatures and durations were used to reproduce the wetting and the consecutive drying step of the wet granulation. Based on the moisture uptake of the excipients and the intermolecular forces built after drying, it was possible to estimate the suitability of excipients to wet or dry granulation and the consequent impact on tableting or capsules/sachet filling processes.
Parameters like surface area, density, particle size and cohesion can be measured with Anton Paar instruments. Knowing these characteristics provides vital information about the most appropriate excipients to use in order to avoid defects which can cause the discharge of the batch at the end of manufacturing. The overview of the principal steps of solid dosage forms manufacturing and the corresponding parameters is presented in Figure 1.