21 CFR § 520.2520a - Trichlorfon and atropine.

---
identifier: "/us/cfr/t21/s520.2520a"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 520.2520a - Trichlorfon and atropine."
title_number: 21
title_name: "Food and Drugs"
section_number: "520.2520a"
section_name: "Trichlorfon and atropine."
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: "520"
part_name: "ORAL DOSAGE FORM NEW ANIMAL DRUGS"
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. 360b."
regulatory_source: "40 FR 13838, Mar. 27, 1975, unless otherwise noted."
cfr_part: "520"
---


# 520.2520a Trichlorfon and atropine.

(a) *Specifications.* (1) For trichlorfon: O,O-Dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate.

(2) For atropine: Atropine N.F.

(b) *Sponsor.* See No. 054771 in § 510.600(c) of this chapter.

(c) *Conditions of use in mice*—(1) *Amount.* Administer 1.67 grams of trichlorfon and 7.7 milligrams of atropine per liter continuously for 7 to 14 days as the sole source of drinking water.

(2) *Indications for use.* For the treatment of *Syphacia obvelata* (pinworm) in laboratory mice.

(3) *Limitations.* Federal law restricts this drug to use by or on the order of a licensed veterinarian.

[79 FR 28832, May 20, 2014]