Critical Process Steps and Control Tests

Critical process steps are operations performed during dosage-form manufacture
that can contribute to variability of the end product if not controlled. Since each
type of dosage form requires different machinery and unit operations to produce
the end product, the critical process steps will also differ. For each product
considered suitable for retrospective validation, a list of these steps must be
compiled following careful analysis of the process by technically competent
persons. In a similar manner, in-process and finished-product tests should be
screened to identify those that may be of some value. As a rule, tests in that the
outcome is quantitative will be of greatest interest.
A flow diagram of the entire operation, but particularly of the manufacturing
process, may be helpful in identifying critical steps, especially where the
process involves many steps. Such a diagram is also a useful addition to the
validation report prepared at the conclusion of the study.