21 CFR § 358.303 - Definitions.

---
identifier: "/us/cfr/t21/s358.303"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 358.303 - Definitions."
title_number: 21
title_name: "Food and Drugs"
section_number: "358.303"
section_name: "Definitions."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "D"
subchapter_name: "DRUGS FOR HUMAN USE"
part_number: "358"
part_name: "MISCELLANEOUS EXTERNAL DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE"
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. 321, 351, 352, 353, 355, 360, 371."
regulatory_source: "55 FR 33255, Aug. 14, 1990, unless otherwise noted."
cfr_part: "358"
---


# 358.303 Definitions.

As used in this subpart:

(a) *Ingrown toenail relief drug product.* A drug product applied to an ingrown toenail that relieves pain or discomfort either by softening the nail or by hardening the nail bed.

(b) *Retainer ring.* A die cut polyethylene foam pad coated on one side with medical grade acrylic pressure-sensitive adhesive. The retainer ring has slots, center-cut completely through the foam with the cut of sufficient size to allow for localization of an active ingredient in a gel vehicle to a specific target area. The retainer ring is used with adhesive bandage strips to place over the retainer ring to hold it in place.