Pharmaceutical scale-up: why multiplying the recipe is not enough

Producing a larger quantity does not necessarily mean repeating the same process in a larger vessel. A change of scale can alter time distributions, mixing and heat transfer. The industrial question is which relationships must remain under control to preserve the product’s characteristics.

The FDA guidance on validation highlights the importance of process knowledge during process design. It does not provide a universal formula for moving from one scale to another.

A transfer that needs documentation

The project team should make differences between equipment and operating conditions explicit. It is useful to distinguish parameters that transfer directly, parameters that need recalculation and aspects requiring experimental verification. The amount of testing depends on available knowledge and risk assessment.

In the editorial example of mixing, keeping the time identical does not demonstrate equivalent behaviour. Process settings need to be linked to measurements relevant to the product, with the interpretation of results defined in advance.

Plan for what does not work, too

An overly rigid industrialisation schedule can make every lesson expensive. The economic plan should allow for tests, analyses and possible adjustments, with progression criteria shared by development, production and quality. Success is not simply obtaining a compliant batch: it means achieving a repeatable, describable process that can be managed by the people who will run it every day.