---
kind: "section"
citation: "21 C.F.R. § 520.2520b"
title: "21"
number: "520.2520b"
heading: "Trichlorfon boluses."
url: "https://uscodex.org/cfr/21/520.2520b"
---

# §520.2520b. Trichlorfon boluses.

- (a) **Specifications.** Each bolus contains either 7.3, 10.9, 14.6, or 18.2 g of trichlorfon.
- (b) **Sponsor.** See No. 054771 in [§ 510.600(c)](/cfr/21/510.600.md?p=c) of this chapter.
- (c) **Conditions of use in horses—**
  - (1) **Amount.** 18.2 milligrams per pound of body weight, except for strongyles use 36.4 milligrams per pound of body weight.
  - (2) **Indications for use.** For horses for removal of bots (Gastrophilus nasalis, Gastrophilus intestinalis), large strongyles (Strongylus vulgaris), small strongyles, large roundworms (ascarids, Parascaris equorum), and pinworms (Oxyuris equi).
  - (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.

## Notes

### Amendments

[45 FR 48127, July 18, 1980. Redesignated and amended at 79 FR 28833, May 20, 2014]

### Authority

Authority: 21 U.S.C. 360b.

### Source

Source: 40 FR 13838, Mar. 27, 1975, unless otherwise noted.

### Amendments

[45 FR 48127, July 18, 1980. Redesignated and amended at 79 FR 28833, May 20, 2014]