---
kind: "section"
citation: "21 C.F.R. § 558.363"
title: "21"
number: "558.363"
heading: "Narasin."
url: "https://uscodex.org/cfr/21/558.363"
---

# §558.363. Narasin.

- (a) **Specifications.** Type A medicated articles containing 36, 45, 54, 72, or 90 grams narasin per pound.
- (b) **Sponsor.** See No. 058198 in [§ 510.600(c)](/cfr/21/510.600.md?p=c) of this chapter.
- (c) **Tolerances.** See [§ 556.428](/cfr/21/556.428.md) of this chapter.
- (d) **Special considerations.** An expiration date of 2 months (8 weeks) is required for narasin Type C medicated swine feeds.
- (e) **Conditions of use.** It is used as follows:
  - (1) **Chickens—**
  - (2) **Swine—**
  - (3) Narasin single-ingredient Type A medicated articles may also be used in combination with:
    - (i) Avilamycin as in [§ 558.68](/cfr/21/558.68.md).
    - (ii) [Reserved]

## Notes

### Amendments

[83 FR 64741, Dec. 18, 2018, as amended at 86 FR 14825, Mar. 19, 2021; 91 FR 20345, Apr. 16, 2026]

### Authority

Authority: 21 U.S.C. 354, 360b, 360ccc, 360ccc-1, 371.

### Source

Source: 40 FR 13959, Mar. 27, 1975, unless otherwise noted.

### Amendments

[83 FR 64741, Dec. 18, 2018, as amended at 86 FR 14825, Mar. 19, 2021; 91 FR 20345, Apr. 16, 2026]