21 CFR § 520.1638 - Oxibendazole.

---
identifier: "/us/cfr/t21/s520.1638"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 520.1638 - Oxibendazole."
title_number: 21
title_name: "Food and Drugs"
section_number: "520.1638"
section_name: "Oxibendazole."
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"
---


# 520.1638 Oxibendazole.

(a) *Specifications.* (1) Each gram of paste contains 227 milligrams (mg) (22.7 percent) oxibendazole.

(2) Each milliliter of suspension contains 100 mg (10 percent) oxibendazole.

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

(c) *Special considerations.* (1) See § 500.25 of this chapter.

(2) Suspension product described in paragraph (a)(2) of this section shall be labeled: “Federal law restricts this drug to use by or on the order of a licensed veterinarian.”

(d) *Conditions of use in horses*—(1) *Amount.* For uses other than for threadworms (*Strongyloides westeri*), 10 mg oxibendazole per kilogram (/kg) body weight; for threadworms (*Strongyloides westeri*), 15 mg/kg. Horses maintained on premises where reinfection is likely to occur should be re-treated in 6 to 8 weeks. Administer suspension product by stomach tube in 3 to 4 pints of warm water, or by top dressing or mixing into a portion of the normal grain ration.

(2) *Indications for use.* For removal and control of large strongyles (*Strongylus edentatus, S. equinus,* *S. vulgaris*); small strongyles (genera *Cylicostephanus, Cylicocyclus,* *Cyathostomum, Triodontophorus,* *Cylicodontophorus,* and *Gyalocephalus*); large roundworms (*Parascaris equorum*); pinworms (*Oxyuris equi*) including various larval stages; and threadworms (*Strongyloides westeri*).

(3) *Limitations.* Do not use in horses intended for human consumption.

[78 FR 28825, May 20, 2014]