21 CFR § 520.35 - Afoxolaner, moxidectin, and pyrantel.

---
identifier: "/us/cfr/t21/s520.35"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 520.35 - Afoxolaner, moxidectin, and pyrantel."
title_number: 21
title_name: "Food and Drugs"
section_number: "520.35"
section_name: "Afoxolaner, moxidectin, and pyrantel."
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"
---


# 520.35 Afoxolaner, moxidectin, and pyrantel.

(a) *Specifications.* Each chewable tablet contains:

(1) 9.375 milligrams (mg) afoxolaner, 45 micrograms (mcg) moxidectin, and 18.75 mg pyrantel (as pamoate salt);

(2) 18.75 mg afoxolaner, 90 mcg moxidectin, and 37.5 mg pyrantel (as pamoate salt);

(3) 37.5 mg afoxolaner, 180 mcg moxidectin, and 75 mg pyrantel (as pamoate salt);

(4) 75 mg afoxolaner, 360 mcg moxidectin, and 150 mg pyrantel (as pamoate salt); or

(5) 150 mg afoxolaner, 720 mcg moxidectin, and 300 mg pyrantel (as pamoate salt).

(b) *Sponsor.* See No. 000010 in § 510.600(c) of this chapter.

(c) *Conditions of use*—(1) *Amount.* Administer orally once a month at the minimum dose of 1.14 mg/lb (2.5 mg/kg) afoxolaner, 5.45 mcg/lb (12 mcg/kg) moxidectin, and 2.27 mg/lb (5.0 mg/kg) pyrantel. For heartworm disease prevention, give once monthly for at least 6 months after last exposure to mosquitoes.

(2) *Indications for use.* For the prevention of heartworm disease caused by *Dirofilaria immitis* and for the treatment and control of adult hookworm (*Ancylostoma caninum, Ancylostoma braziliense,* and *Uncinaria stenocephala*) and roundworm (*Toxocara canis* and *Toxascaris leonina*) infections. Kills adult fleas and is indicated for the treatment and prevention of flea infestations (*Ctenocephalides felis*) and the treatment and control of *Ixodes scapularis* (black-legged tick), *Rhipicephalus sanguineus* (brown dog tick), *Dermacentor variabilis* (American dog tick), *Amblyomma americanum* (lone star tick), and *Haemaphysalis longicornis* (longhorned tick) infestations for 1 month in dogs and puppies 8 weeks of age and older, weighing 4 pounds of body weight or greater. For the prevention of *Borrelia burgdorferi* infections as a direct result of killing *Ixodes scapularis* vector ticks.

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

[88 FR 84699, Dec. 6, 2023, as amended at 90 FR 6799, Jan. 21, 2025; 90 FR 40969, Aug. 22,2025]