21 CFR 211.170
Reserve samples
21 CFR 211.170 is the regulation titled “Reserve samples” in 21 CFR Part 211, Current Good Manufacturing Practice for Finished Pharmaceuticals. Since 2021, 6 FDA warning letters have cited it.
- Letters citing it
- 6 since 2021
- Jan 1 to Oct 30, 2026
- 1 against 1 on the same dates in 2025
- Most often cited with
- 21 CFR 211.165, in 5 letters
- Closed out
- 0% of these letters have a published close-out
Letters citing it, by year issued
Most are drug letters (5 of 6). 2026 runs to Oct 30, 2026. Pick a year to see its letters.
The regulation
Read the text of 21 CFR 211.170 (eCFR, as of Sep 1, 2026)
(a) An appropriately identified reserve sample that is representative of each lot in each shipment of each active ingredient shall be retained. The reserve sample consists of at least twice the quantity necessary for all tests required to determine whether the active ingredient meets its established specifications, except for sterility and pyrogen testing. The retention time is as follows:
(1) For an active ingredient in a drug product other than those described in paragraphs (a) (2) and (3) of this section, the reserve sample shall be retained for 1 year after the expiration date of the last lot of the drug product containing the active ingredient.
(2) For an active ingredient in a radioactive drug product, except for nonradioactive reagent kits, the reserve sample shall be retained for:
(i) Three months after the expiration date of the last lot of the drug product containing the active ingredient if the expiration dating period of the drug product is 30 days or less; or
(ii) Six months after the expiration date of the last lot of the drug product containing the active ingredient if the expiration dating period of the drug product is more than 30 days.
(3) For an active ingredient in an OTC drug product that is exempt from bearing an expiration date under § 211.137, the reserve sample shall be retained for 3 years after distribution of the last lot of the drug product containing the active ingredient.
(b) An appropriately identified reserve sample that is representative of each lot or batch of drug product shall be retained and stored under conditions consistent with product labeling. The reserve sample shall be stored in the same immediate container-closure system in which the drug product is marketed or in one that has essentially the same characteristics. The reserve sample consists of at least twice the quantity necessary to perform all the required tests, except those for sterility and pyrogens. Except for those for drug products described in paragraph (b)(2) of this section, reserve samples from representative sample lots or batches selected by acceptable statistical procedures shall be examined visually at least once a year for evidence of deterioration unless visual examination would affect the integrity of the reserve sample. Any evidence of reserve sample deterioration shall be investigated in accordance with § 211.192. The results of the examination shall be recorded and maintained with other stability data on the drug product. The retention time is as follows:
(1) For a drug product other than those described in paragraphs (b) (2) and (3) of this section, the reserve sample shall be retained for 1 year after the expiration date of the drug product.
(2) For a radioactive drug product, except for nonradioactive reagent kits, the reserve sample shall be retained for:
(i) Three months after the expiration date of the drug product if the expiration dating period of the drug product is 30 days or less; or
(ii) Six months after the expiration date of the drug product if the expiration dating period of the drug product is more than 30 days.
(3) For an OTC drug product that is exempt for bearing an expiration date under § 211.137, the reserve sample must be retained for 3 years after the lot or batch of drug product is distributed.
[48 FR 13025, Mar. 29, 1983, as amended at 60 FR 4091, Jan. 20, 1995; 89 FR 51770, June 18, 2024]
Text from eCFR as of Sep 1, 2026.
Cited alongside it
Regulations that appear in the same letters as 21 CFR 211.170.
- 21 CFR 211.165Testing and release for distribution5 letters cite both
- 21 CFR 211.137Expiration dating4 letters cite both
- 21 CFR 211.84Testing and approval or rejection of components, drug product containers, and closures4 letters cite both
- 21 CFR 211.180General requirements3 letters cite both
- 21 CFR 211.188Batch production and control records3 letters cite both
- 21 CFR 211.22Responsibilities of quality control unit3 letters cite both
- 21 CFR 211.100Written procedures; deviations2 letters cite both
- 21 CFR 211.166Stability testing2 letters cite both
Latest letters citing it
The 3 letters citing 21 CFR 211.170 that FDA posted most recently.
- DrugsView Lexia LLCOTC drug products, including an OTC topical pain relief productIssuedApr 7, 2026PostedApr 28, 2026
- DrugsView Huangshi Hygienic Material Medicine Co., Ltd.Over-the-counter drug products manufactured for the U.S. marketIssuedMar 24, 2025PostedJun 3, 2025
- BiologicsView Regenerative Processing Plant, LLCRegener-Eyes PRO and LITE ophthalmic solutionsIssuedAug 16, 2024PostedSep 6, 2024
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Counts include every citation in a letter, as the Letters filter does. How this database is built.