The number of single pot systems used for the production of granules for solid drugs is increasing continuously worldwide. Even if ‘single pot system‘ has now become an accepted term, it may be helpful to specify, though, that the single pot system referred to in this paper always consists of a mixer/granulator and a dryer incorporated in one vessel.
The first single pot units were mixer/granulators retrofitted for vacuum drying. The energy needed for drying was provided by heated jacket water. However, the single-pot system was only accepted by the pharmaceutical industry when drying times were reduced dramatically by microwave
(1987) or by gas (1989) assistance. A number of different reasons exist why single pot technology is selected for the production of granules:
- The yield of modern production-scale single-pot systems is far in excess of 99%.
- Organic solvents can be recovered relatively easily, as it is only necessary to treat the pure
solvent vapour rather than a large air flow with a small organic solvent concentration as in the case of the fluidized bed process. As the granules are dried in a vacuum atmosphere containing practically no oxygen, the explosion risk is also reduced substantially.
- Where highly active substances are handled, the one-pot process allows a relatively easy
protection of the environment because of the fully contained design and the integrated
cleaning-in-place systems.
- One-pot units can be used for the aseptic production of granules since the process is fully contained and an additional sterilizingin- place system can be installed.
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