Product and process validation

Different types of validation strategies are available:

Prospective validation (recommended): To be performed during the product development, prior to the manufacture of finished product that is intended for sale.
Concurrent validation: In exceptional circumstances it may be acceptable not to complete a validation program before routine production starts, but during routine production. It is important that the premises and equipment to be used have been validated.
Retrospective validation: Validation of a process for a product already in distribution based upon accumulated production, testing and historical control data.
Revalidation: Revalidation establishes that a changed process or product meets all functional and safety requirements, two categories exist:
Revalidation in case of known change (change control system)
Periodic revalidation carried out at scheduled intervals, as defined in the individual validation reports or Validation Master Plan

Product Validation Process steps sequence:

Process FMEA: A systematic identification and analysis of the potential process failure modes and causes, and an analysis of the associated risk.
Validation Master Plan (VMP): A VMP shall represent an overview of the entire validation operation (including facility).
Facility qualification: Establishing by objective evidence that the facility, its infrastructure and ancillary systems are capable of constantly meeting its pre-determined requirements.
Equipment Installation (IQ) and Operational Qualification (OQ): Establishing by objective evidence that all key aspects of the process equipment and ancillary systems (including software) are capable of consistently operating within established limits and tolerances
Screening experiment, Design of Experiment: To identify the key variables for the process. This experiment can be skipped if critical process factors are known.
Process (performance) Qualification (PQ): Establishing confidence that the process is effective and reproducible.
Product performance Qualification: Establishing documented evidence through appropriate testing that the finished product produced by a specified process(es) meets all release requirements (design specification) for functionality and safety.
Product monitoring and maintenance: Establishing by objective evidence that trends in the process were monitored to ensure the process remains within the established process limits.