{"id":19792,"date":"2026-06-23T08:00:00","date_gmt":"2026-06-23T08:00:00","guid":{"rendered":"https:\/\/www.thermofisher.com\/blog\/behindthebench\/?p=19792"},"modified":"2026-06-04T20:52:11","modified_gmt":"2026-06-04T20:52:11","slug":"reducing-discontinuities-in-pharmaceutical-scale-up","status":"publish","type":"post","link":"https:\/\/www.thermofisher.com\/blog\/behindthebench\/reducing-discontinuities-in-pharmaceutical-scale-up\/","title":{"rendered":"Reducing Discontinuities in Pharmaceutical Scale-Up"},"content":{"rendered":"\n
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Overview<\/h2>\n\n\n\n

Successful pharmaceutical scale-up depends on more than increased production capacity. Continuity across processing parameters or the geometry of equipment is essential. Scale-up challenges often arise when multiple geometric and operational changes are introduced simultaneously, making it difficult to identify the sources of variability. If the material\u2019s processing environment changes, outcomes may be different than what is desired, even when operating conditions appear proportionally scaled. Predictable scale-up is achieved by deliberately preserving key process drivers, introducing changes incrementally, and aligning critical parameters across different scales. By minimizing discontinuities, manufacturers can improve process predictability and ensure consistent product performance from development through commercial production.<\/p>\n<\/div>\n\n\n\n

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Why continuity across equipment, parameters, and unit operations determines success<\/h2>\n\n\n\n

Scale-up rarely fails because a process is fundamentally unsound. More often, challenges arise when modifications are introduced to the pharmaceutical production process without fully accounting for those changes\u2019 consequences. When using twin-screw extruders<\/a>\u00a0 in pharmaceutical manufacturing<\/a>, the equipment size may be increased, or the feeding configuration may change, or downstream handling may be adjusted. While each of these transitions could be reasonable on its own, when implemented together their cumulative impact can make the root-cause identification of scale-up failures significantly more complex.<\/p>\n\n\n\n

The issue is not scaling itself. It is the discontinuities introduced during scaling.<\/p>\n\n\n\n

As development progresses from laboratory to pilot scale and eventually to production, transitions are inevitable: Throughput increases; equipment geometry changes; unit operations evolve. Each transition alters the physical or operational environment in which the material is processed. Predictable scale-up depends on managing each modification deliberately.
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Physical discontinuities: When size alters behavior<\/h2>\n\n\n\n

One of the most common discontinuities arises when moving between extruder sizes. Understanding this is not meant to discourage scaling, but to clarify where careful attention is required.<\/p>\n\n\n\n

As screw diameter increases, surface area increases with the square of the diameter, while material volume increases with the cube. Thus the ratio between thermal exchange surface and material mass shifts too. In larger systems, less surface area is available per unit volume to introduce or remove heat.<\/p>\n\n\n\n

A useful way to consider how this affects scale-up is to imagine two systems operating at proportionally similar setpoints. On paper, screw speed and feed rate may appear correctly scaled. Yet inside the barrel, the larger system retains heat differently and distributes mechanical energy differently. From the material\u2019s perspective, the environment is not identical, even if the numerical settings are.<\/p>\n\n\n\n

In controlled scale-up investigations across geometrically similar 11 mm, 16 mm, and 24 mm twin-screw extruders, it has been shown that maintaining comparable mean residence time and specific mechanical energy consumption results in closely aligned process behavior across scales. However, these parameters do not remain constant automatically when diameter changes. They must be adjusted intentionally.<\/p>\n\n\n\n

If feed rate is increased according to geometric scaling alone, residence time distribution may shift. If screw speed is not modified appropriately, specific mechanical energy may change, influencing melt temperature and mixing intensity.<\/p>\n\n\n\n

In practice, these differences rarely present as immediate failures. Instead, a process that once operated comfortably within its design window may begin to require tighter control. Dissolution may remain within specification, but variability increases. Operators may find that small parameter adjustments produce larger effects than before.<\/p>\n\n\n\n

When the extruder size changes, surface area and volume change at different rates, and the physical relationships governing the process change too. The practical response is not to avoid scaling, but to identify which parameters must be preserved to recreate the same material experience.<\/p>\n\n\n\n

Process discontinuities: When workflow changes accumulate<\/h2>\n\n\n\n

Not all discontinuities are geometric. Many are operational.<\/p>\n\n\n\n

Here are just a few examples of minor operational changes that could have an outsized effect: <\/p>\n\n\n\n