Change management As Per WHO TRS1019 Annex 3
Manufacturers should follow change-control procedures when changes are planned to existing systems or processes. The change-control procedure and records should ensure that all aspects are thoroughly documented and approved,
including regulatory approval where appropriate (variation).
Sufficient data should be generated to demonstrate that the revised process will result in a product of the desired quality, consistent with approved specifications.

Validation should be considered when changes to production and/or control procedures are planned. Based on risk assessment, changes that may require revalidation could include (but are not limited to):
- Changes in the master formula, methods, starting material manufacturer, starting material manufacturing process, excipient manufacturer, and excipient manufacturing process.
- Changes in the equipment or instruments (e.g. addition of automatic detection systems).
- Changes associated with equipment calibrations and the preventive maintenance carried out may impact the process.
- production area and support system changes (e.g.re-arrangement of areas or a new water-treatment method).
- Changes in the manufacturing process (e.g. mixing times, drying temperatures).
- Transfer of processes to another site.
- Unexpected changes (e.g. those observed during self-inspection or during routine analysis of process trend data).
- Changes to standard operating procedures.
- Changes to cleaning and hygiene programmes.
Depending upon the nature of the change being proposed, the change control process should consider whether existing approved specifications will be adequate to control the product subsequent to the implementation of the change.
Reference: Good manufacturing practices: guidelines on validation -Annex 3