21 CFR 211.110 - Sampling and Testing of In-Process Materials and Drug Products

What it says

Written procedures must describe in-process sampling and testing, including control procedures to monitor process output and validate the performance of manufacturing processes that may be responsible for causing variability in the characteristics of in-process material and the drug product.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• In-process controls under this provision function as an early-warning system, catching a drifting process before it produces an out-of-specification finished batch, rather than relying solely on final release testing.
• This provision explicitly connects in-process sampling to process validation, meaning in-process control data is frequently among the key evidence used to demonstrate a manufacturing process remains in a validated state.
• Where in-process controls are set too loosely to actually detect meaningful process variability, they can create a false sense of control that later surfaces as a finished-product failure.

What FDA inspectors look for

• Whether written in-process sampling and testing procedures exist and are actually followed at the specified points in the manufacturing process.
• Whether in-process control limits are scientifically justified and tight enough to meaningfully detect process variability, rather than set so broadly that they cannot fail.
• Whether in-process test results are reviewed and trended over time to identify gradual process drift, not just checked pass or fail against a single batch's limits.

Related regulations