Quality assurance in pharmaceutical powder processing: Current developments

Pharmacopoeia1 requirements relating to standardization of the physical performance of oral dosage forms containing powders are usually limited to tests on the final product.

Such tests are aimed at ensuring that all tablets or capsules have the correct, nominal, drug content and that the drug is released into solution within a specified time. Whilst dissolution or disintegration test to assess drug release can only be carried out on a finished dosage form, content uniformity tests currently carried out on tablets or capsules alone could also be usefully carried out earlier on component powders at different stages during processing. The aim of developing a quality assurance procedure for quantifying the homogeneity of powders prior to tablet compaction or encapsulation would be to pin-point more precisely the part of a process where content uniformity problems arise. Secondly, a good quality assurance procedure would provide full mechanistic information about the behaviour of a given powder system, so that appropriate remedies could be applied.

Eleven different methods of testing homogeneity of powder mixes have been cited in pharmaceutically oriented literature and these will be reviewed in terms of their usefulness as routine quality assurance procedures for drug content uniformity. Of these 11 methods, 2 test methods were considered to be especially useful: one based on a flow test and the other on vibration analysis. This techniques has been validated using a complete vibration analysis and testing rig under conditions encountered during routine powder processing.

It would be desirable to see standard powder mixes tested on apparatus of the same design in different laboratories as a means of assessing the reproducibility of the proposed quality assurance method when used by different personnel.