21 CFR § 556.283 - Florfenicol.

---
identifier: "/us/cfr/t21/s556.283"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 556.283 - Florfenicol."
title_number: 21
title_name: "Food and Drugs"
section_number: "556.283"
section_name: "Florfenicol."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "E"
subchapter_name: "ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS"
part_number: "556"
part_name: "TOLERANCES FOR RESIDUES OF NEW ANIMAL DRUGS IN FOOD"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 342, 360b, 371."
regulatory_source: "84 FR 32993, July 11, 2019, unless otherwise noted."
cfr_part: "556"
---


# 556.283 Florfenicol.

(a) *Acceptable daily intake (ADI).* The ADI for total residue of florfenicol is 10 µg/kg of body weight per day.

(b) *Tolerances.* The tolerances for florfenicol amine (marker residue) are:

(1) *Cattle.* (i) Liver (target tissue): 3.7 ppm.

(ii) Muscle: 0.3 ppm.

(2) *Swine.* (i) Liver (target tissue): 2.5 ppm.

(ii) Muscle: 0.2 ppm.

(3) *Catfish.* Muscle (target tissue): 1 ppm.

(4) *Freshwater-reared warmwater finfish (other than catfish) and salmonids.* Muscle/skin (target tissue): 1 ppm.

(c) *Related conditions of use.* See §§ 520.955, 522.955, 522.956, and 558.261 of this chapter.