Comparative Study of Glidant Mixing Processes for Direct Compression

Direct compression is a faster, simpler, and easier technique for tablet manufacturing compared to other processes such as wet and dry granulation techniques. Glidants are often incorporated in direct compression formulations to improve powder flow. However, poor enhancement of powder flow leads to abandon the direct compression and apply the granulation process. The direct compression formulation is usually composed of micronized active pharmaceutical ingredient (API) and enlarged direct compression vehicles. Appropriate mixing of glidant is important to coat entire surface of the micronized particle as well as the enlarged particles with glidant and to obtain the glidant action.

In order to improve the powder flow of direct compression formulation, we have proposed that mixing of glidant and lubricant is divided into two processes for micronized API and enlarged direct compression excipients, and have compared three mixing approaches; one-step mixing, two-step glidant mixing and two-step glidant and lubricant mixing.

In the one-step mixing, API, direct compression excipients, lubricant and glidant were mixed all in one-step operation. For the two-step glidant mixing, glidant mixing was split to two independent steps; glidant was mixed with API, another glidant was mixed with direct compression excipients and lubricant, and the two mixed powders were blended for tabletting. In the two-step glidant and lubricant mixing, addition of lubricant was also divided into two mixing processes; glidant and lubricant were mixed with API, another glidant and lubricant were mixed with direct compression excipients, and the two mixtures were blended.

Addition of glidant improved the powder flow properties and tablet properties, whichever mixing process was applied, as compared with direct compression formulation excluding glidant. The one-step mixing indicated poor improvement of flow properties, although favorable enhancement of mechanical strength of tablet. Conversely, the two-step glidant mixing showed excellent improvement of flow properties, although poor enhancement of tablet hardness. The two-step glidant and lubricant mixing indicated good powder flow and tablet properties. Results demonstrated that mixing processes of glidant and lubricant have impacts on the powder flow and tablet properties.

Key Words: Glidant, Powder Flow Properties, Tablet Properties, Direct Compression, Lubricant