21 CFR § 524.660 - Dimethyl sulfoxide.

---
identifier: "/us/cfr/t21/s524.660"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 524.660 - Dimethyl sulfoxide."
title_number: 21
title_name: "Food and Drugs"
section_number: "524.660"
section_name: "Dimethyl sulfoxide."
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: "524"
part_name: "OPHTHALMIC AND TOPICAL 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 13873, Mar. 27, 1975, unless otherwise noted."
cfr_part: "524"
---


# 524.660 Dimethyl sulfoxide.

(a) *Specifications.* (1) Each milliliter (mL) of solution contains 90 percent dimethyl sulfoxide and 10 percent water.

(2) Each milliliter (mL) of gel product contains 90 percent dimethyl sulfoxide.

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

(c) *Conditions of use in horses and dogs*—(1) *Amount*—(i) *Horses.* Apply topically two to three times daily in an amount not to exceed 100 mL per day. Total duration of therapy should not exceed 30 days.

(ii) *Dogs.* Apply topically three to four times daily in an amount not to exceed 20 mL per day. Total duration of therapy should not exceed 14 days.

(2) *Indications for use.* To reduce acute swelling due to trauma.

(3) *Limitations.* Do not use in horses intended for human consumption. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

[79 FR 10967, Feb. 27, 2014]