21 CFR 58.113
Mixtures of articles with carriers
21 CFR 58.113 is the regulation titled “Mixtures of articles with carriers” in 21 CFR Part 58, Good Laboratory Practice for Nonclinical Laboratory Studies. Since 2021, 1 FDA warning letter has cited it.
- Letters citing it
- 1 since 2021
- Jan 1 to Oct 30, 2026
- 1 against 0 on the same dates in 2025
- Most often cited with
- 21 CFR 58.31, in 1 letter
- Closed out
- 0% of these letters have a published close-out
Letters citing it, by year issued
It is a drug letter. 2026 runs to Oct 30, 2026. Pick a year to see its letters.
- 02021
- 02022
- 02023
- 02024
- 02025
- 12026
What FDA writes when it cites it
The finding headings that cite 21 CFR 58.113 most often, as written in the letters.
- 1 letterFailure of the testing facility management to assure that tests for mixtures of articles with carriers were conducted by appropriate analytical methods to determine the uniformity of the mixture and the concentration of…
The regulation
Read the text of 21 CFR 58.113 (eCFR, as of Sep 1, 2026)
(a) For each test or control article that is mixed with a carrier, tests by appropriate analytical methods shall be conducted:
(1) To determine the uniformity of the mixture and to determine, periodically, the concentration of the test or control article in the mixture.
(2) To determine the stability of the test and control articles in the mixture as required by the conditions of the study either:
(i) Before study initiation, or
(ii) Concomitantly according to written standard operating procedures which provide for periodic analysis of the test and control articles in the mixture.
(b) [Reserved]
(c) Where any of the components of the test or control article carrier mixture has an expiration date, that date shall be clearly shown on the container. If more than one component has an expiration date, the earliest date shall be shown.
[43 FR 60013, Dec. 22, 1978, as amended at 45 FR 24865, Apr. 11, 1980; 52 FR 33781, Sept. 4, 1987]
Text from eCFR as of Sep 1, 2026.
Cited alongside it
Regulations that appear in the same letters as 21 CFR 58.113.
Latest letters citing it
The letter citing 21 CFR 58.113 that FDA posted most recently.
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