---
kind: "section"
citation: "21 C.F.R. § 520.48"
title: "21"
number: "520.48"
heading: "Altrenogest."
url: "https://uscodex.org/cfr/21/520.48"
---

# §520.48. Altrenogest.

- (a) **Specifications.** Each milliliter (mL) of solution contains 2.2 milligrams (mg) altrenogest.
- (b) **Sponsors.** See sponsors in [§ 510.600(c)](/cfr/21/510.600.md?p=c) of this chapter:
  - (1) **Nos.** 000061 and 051072 for use as in [paragraph (d)](#d) of this section.
  - (2) **No.** 061133 for use as in [paragraph (d)(1)](#d-1) of this section.
  - (3) **No.** 053701 for use as in [paragraph (d)(2)](#d-2) of this section.
- (c) **Tolerances.** See [§ 556.36](/cfr/21/556.36.md) of this chapter.
- (d) **Conditions of use—**
  - (1) **Horses—**
    - (i) **Amount.** 1.0 mL per 110 pounds body weight (0.044 mg/kg) daily for 15 consecutive days.
    - (ii) **Indications for use.** For suppression of estrus in mares.
    - (iii) **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.
  - (2) **Swine—**
    - (i) **Amount.** Administer 6.8 mL (15 mg altrenogest) per gilt once daily for 14 consecutive days by top-dressing on a portion of each gilt's daily feed.
    - (ii) **Indications for use.** For synchronization of estrus in sexually mature gilts that have had at least one estrous cycle.
    - (iii) **Limitations.** Do not use in gilts having a previous or current history of uterine inflammation (i.e., acute, subacute or chronic endometritis). Gilts must not be slaughtered for human consumption for 21 days after the last treatment.

## Notes

### Amendments

[66 FR 47960, Sept. 17, 2001, as amended at 68 FR 62006, Oct. 31, 2003; 72 FR 9455, Feb. 21, 2008; 74 FR 61516, Nov. 25, 2009; 77 FR 32012, May 31, 2012; 80 FR 34278, June 16, 2015; 82 FR 21690, May 10, 2017; 83 FR 13635, Mar. 30, 2018; 84 FR 8972, Mar. 13, 2019; 88 FR 27698, May 3, 2023; 91 FR 20340, Apr. 16, 2026]

### Authority

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

### Source

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

### Amendments

[66 FR 47960, Sept. 17, 2001, as amended at 68 FR 62006, Oct. 31, 2003; 72 FR 9455, Feb. 21, 2008; 74 FR 61516, Nov. 25, 2009; 77 FR 32012, May 31, 2012; 80 FR 34278, June 16, 2015; 82 FR 21690, May 10, 2017; 83 FR 13635, Mar. 30, 2018; 84 FR 8972, Mar. 13, 2019; 88 FR 27698, May 3, 2023; 91 FR 20340, Apr. 16, 2026]