Process validation, the three-stage proof FDA expects behind every batch

In fiscal 2025, FDA investigators cited 21 CFR 211.100(a) 162 times on Form 483 reports at drug sites under the heading "Absence of Written Procedures," making it the third most-cited drug observation of the year, according to the agency's fiscal 2025 inspection observation file¹. The regulation requires written procedures for production and process control. Its neighbor, section 211.110(a), which requires controls that "validate the performance" of manufacturing steps, drew 36 citations under its main heading.

Those two sections are the legal foundation of process validation, according to FDA's January 2011 guidance³ on the subject. The guidance, announced in a Federal Register notice⁴ that month, "revises and replaces" a guideline FDA issued in May 1987. It recast validation as a three-stage program that starts in development and runs for as long as a product is made.

Process validation is how a factory shows that the 10,000th batch of a tablet matches the first. That question weighs heavily on generics, many of them older products made in large volumes. This piece explains the three stages, the persistent myth that three batches are enough, and how validation gaps show up in inspections and recalls.

The legal hook

Section 211.100(a)⁵ says there "shall be written procedures for production and process control" that assure drug products "have the identity, strength, quality, and purity they purport or are represented to possess." Section 211.100(b) says the procedures must be followed and documented as the work is done, and that "any deviation from the written procedures shall be recorded and justified."

Section 211.110⁶ adds the in-process piece. Its paragraph (a) requires control procedures "to monitor the output and to validate the performance of those manufacturing processes that may be responsible for causing variability," listing checks such as tablet weight variation, disintegration time, mixing adequacy, dissolution and bioburden. Paragraph (b) says in-process specifications must be consistent with final specifications and "derived from previous acceptable process average and process variability estimates where possible."

The 2011 guidance builds on those two sections and defines process validation as "the collection and evaluation of data, from the process design stage through commercial production, which establishes scientific evidence that a process is capable of consistently delivering quality product." One premise runs through the document. "Quality cannot be adequately assured merely by in-process and finished-product inspection or testing," it says. Tests look at samples, and a process that drifts can turn out units the samples miss.

Three stages

Stage 2 is the gate. The guidance says a manufacturer "must successfully complete PPQ before commencing commercial distribution," and that PPQ will usually involve "a higher level of sampling, additional testing, and greater scrutiny" than routine production. The protocol has to fix sampling points, sample counts and statistical methods in advance, and data "should not be excluded" without a documented, science-based reason. For nonconforming results, the guidance points to FDA's separate guidance on out-of-specification results¹⁴, which our OOS explainer covers.

Stage 3 rests on an older rule. Section 211.180(e)⁷ requires that records be kept so their data can be used to evaluate each product's quality standards "at least annually." The guidance asks for more: data "statistically trended and reviewed by trained personnel," a statistician or similarly trained person to design the plan, and scrutiny of variation both within a batch and between batches.

The three-batch myth

For years, the industry rule of thumb was that three good full-scale batches validated a process. FDA has rejected that. In its CGMP questions and answers on production and process controls⁸, the agency says: "Neither the CGMP regulations nor FDA policy specifies a minimum number of batches to validate a manufacturing process." It adds that validation "cannot be reduced to so simplistic a formula as the completion of three successful full-scale batches," and acknowledges that "the idea of three validation batches became prevalent in part because of language used in past Agency guidance." The manufacturer is expected "to have a sound rationale" for its choice.

Shipping before validation is finished is allowed only rarely. The 2011 guidance describes "concurrent release," in which a PPQ batch is distributed before the protocol is complete, and says FDA "expects that concurrent release will be used rarely." Its examples include drugs with limited demand such as orphan drugs, short-lived radiopharmaceuticals, and medically necessary drugs "being manufactured in coordination with the Agency to alleviate a short supply."

Old products, current rules

A large share of the generic supply predates the current approach. FDA approved 7,388 original generic applications from 1984 through 2010, according to GxRadar's count of Drugs@FDA data¹³ on our approvals page. The 2011 guidance speaks to older products directly. For "legacy products," it says, implementation "would likely begin with the activities described in Stage 3," using manufacturing experience to improve the process. It also makes a supply argument for the whole exercise: validation "offers assurance that a process is reasonably protected against sources of variability that could affect production output, cause supply problems, and negatively affect public health." That link to supply is one reason quality problems show up on FDA's shortage list, as our piece on shortage causes explains.

Recall records rarely name validation outright. Of 18,076 drug recall records published since June 2012, 195 use the word in their reason, and 166 of those, all reported in 2023, concerned missing validation data for sanitization or decontamination cycles, according to GxRadar's analysis of openFDA¹². A broader label is far more common. From January 2024 through Oct. 28, 2026, 609 of 2,126 drug recall records, or 29 percent, used the phrase "CGMP deviations." FDA's FY2024 quality report¹¹ found that recalls tied to CGMP deficiencies made up about half of recalls from fiscal 2020 through 2023 but 24 percent in fiscal 2024. Our CGMP explainer and our guide to 483s and warning letters describe how such findings are written up.

Source: GxRadar totals across all citation headings for each section in FDA's inspection observation spreadsheets, posted on the agency's inspection observations page². The files cover 483s generated by FDA's electronic system, so some manually prepared 483s are missing.

What is changing

Section 211.110 is now getting guidance of its own. FDA published a draft guidance⁹ on complying with it, announced in the Federal Register¹⁰ on Jan. 6, 2025. FDA says that when final it will describe how to meet the batch uniformity requirements, cover quality considerations for drugs made with advanced manufacturing, and explain how manufacturers can build process models into their commercial control strategies. Our coverage of continuous manufacturing and FDA's quality management maturity program follows the related efforts. The draft was still listed for comment under docket FDA-2024-D-5374 when this was written.