21 CFR § 558.254 - Famphur.
---
identifier: "/us/cfr/t21/s558.254"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 558.254 - Famphur."
title_number: 21
title_name: "Food and Drugs"
section_number: "558.254"
section_name: "Famphur."
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: "558"
part_name: "NEW ANIMAL DRUGS FOR USE IN ANIMAL FEEDS"
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. 354, 360b, 360ccc, 360ccc-1, 371."
regulatory_source: "40 FR 13959, Mar. 27, 1975, unless otherwise noted."
cfr_part: "558"
---
# 558.254 Famphur.
(a) *Specifications.* Type A medicated articles containing 13.2 or 33.3 percent famphur.
(b) *Sponsor.* See No. 000061 in § 510.600(c) of this chapter.
(c) *Related tolerances.* See § 556.273 of this chapter.
(d) *Special considerations.* Famphur is a cholinesterase inhibitor. Do not use this product in animals simultaneously or within a few days before or after treatment with or exposure to cholinesterase-inhibiting drugs, pesticides, or chemicals.
(e) *Conditions of use.* It is used in cattle feed as follows:
| Famphur amount | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- |
| (1) To provide 1.1 milligrams per pound (mg/lb) body weight per day | Beef cattle and nonlactating dairy cattle: For control of grubs and as an aid in control of sucking lice | Feed for 30 days. Withdraw from dry dairy cows and heifers 21 days prior to freshening. Withdraw 4 days prior to slaughter | 000061 |
| (2) To provide 2.3 mg/lb body weight per day | Beef cattle and nonlactating dairy cattle: For control of grubs | Feed for 10 days. Withdraw from dry dairy cows and heifers 21 days prior to freshening. Withdraw 4 days prior to slaughter | 000061 |
[84 FR 39185, Aug. 9, 2019, as amended at 87 FR 17947, Mar. 29, 2022]