When FDA finds that a manufacturer has significantly violated FDA regulations, FDA notifies the manufacturer. This notification is often in the form of a Warning Letter. 


The Warning Letter identifies the violation, such as poor manufacturing practices, problems with claims for what a product can do, or incorrect directions for use. 


The letter also makes clear that the company must correct the problem and provides directions and a time frame for the company to inform FDA of its plans for correction. FDA then checks to ensure that the company’s corrections are adequate. 


Matters described in FDA warning letters may have been subject to subsequent interaction between FDA and the recipient of the letter that may have changed the regulatory status of the issues discussed in the letter.


In the period FY2017 - FY2021  The Top 10 Drug Warning Letters were:

1 — 21 CFR 211.22(d) — Quality control unit procedures (written and followed)

2 — 21 CFR 211.192 — Investigations of discrepancies

3 — 21 CFR 211.160(b) — Lab controls (should include scientifically sound specifications)

4 — 21 CFR 211.100(a) — Written procedures for Production and Process Controls

5 — 21 CFR 211.25(a) — Personnel qualifications (education, training, and experience, or any combination thereof)

6 — 21 CFR 211.68(b) — Automatic, mechanical, and electronic equipment (Appropriate controls shall be exercised over computer or related systems to assure that changes in master production and control records or other records are instituted only by authorized personnel)

7 — 21 CFR 211.166(a) — Stability testing (A stability testing program shall be written and used)

8 — 21 CFR 211.67(b)— Equipment cleaning and maintenance (Written procedures shall be established and followed for cleaning and maintenance of equipment)

9 — 21 CFR 211.67(a) — Equipment cleaning and maintenance (Equipment and utensils shall be cleaned, maintained, and, as appropriate for the nature of the drug, sanitized and/or sterilized at appropriate intervals)

10 — 21 CFR 211.110(a) — Sampling and testing of in-process materials and drug products (Written procedures shall be established and followed that describe the in-process controls, and tests, or examinations to be conducted on appropriate samples of in-process materials of each batch)