21 CFR § 520.443 - Chlortetracycline tablets and boluses.

---
identifier: "/us/cfr/t21/s520.443"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 520.443 - Chlortetracycline tablets and boluses."
title_number: 21
title_name: "Food and Drugs"
section_number: "520.443"
section_name: "Chlortetracycline tablets and boluses."
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"
---


# 520.443 Chlortetracycline tablets and boluses.

(a) *Specifications.* Each tablet contains 25 milligrams (mg) chlortetracycline hydrochloride; each bolus contains 250 or 500 mg chlortetracycline hydrochloride.

(b) *Sponsors.* See sponsors in § 510.600(c) of this chapter for use as in paragraph (d) of this section.

(1) No. 069043 for use of a 250-mg bolus as in paragraph (d)(1) of this section.

(2) No. 016592 for use of a 25-mg tablet as in paragraph (d)(2) of this section.

(3) No. 016592 for use of a 500-mg bolus as in paragraph (d)(3) of this section.

(c) *Related tolerances.* See § 556.150 of this chapter.

(d) *Conditions of use in calves*—(1) *Amount.* One 250 milligram bolus per 50 pounds of body weight twice a day for 3 to 5 days.

(i) *Indications for use.* Treatment of bacterial enteritis (scours) caused by *Escherichia coli* and bacterial pneumonia associated with *Pasteurella* spp., *Klesbsiella* spp., and *Haemophilus* spp.

(ii) *Limitations.* Administer bolus directly by mouth or crush and dissolve in milk or water for drenching or bucket feeding. Do not use for more than 5 days. Do not administer within 24 hours of slaughter. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

(2) *Amount.* One 25 milligram tablet for each 5 pounds of body weight every 12 hours daily for 3 to 5 days.

(i) *Indications for use.* Control and treatment of bacterial enteritis (scours) caused by *E. coli* and *Salmonella* spp. And bacterial pneumonia associated with *Pasteurella* spp., *Haemophilus* spp., and *Klebsiella* spp., susceptible to chlortetracycline.

(ii) *Limitations.* Administer tablet directly by mouth or crush and dissolve in water for drenching; if no improvement is noted after 3 days of treatment, consult a veterinarian; do not use for more than 5 days; when feeding milk or milk replacer, administration 1 hour before or 2 hours after feeding; do not administer within 24 hours of slaughter. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

(3) *Amount.* One 500 milligram bolus per 100 pounds of body weight twice a day for 3 to 5 days.

(i) *Indications for use.* Treatment of bacterial enteritis (scours) caused by *E. coli* and *Salmonella* spp., and bacterial pneumonia associated with *Pasteurella* spp., *Haemophilus* spp., and *Klebsiella* spp., susceptible to chlortetracycline.

(ii) *Limitations.* Do not use for more than 5 days. Do not administer within 24 hours of slaughter. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

[57 FR 37325, Aug. 18, 1992, as amended at 67 FR 78355, Dec. 24, 2002. Redesignated and amended at 76 FR 49649, Aug. 11, 2011; 78 FR 21059, Apr. 9, 2013; 81 FR 17607, Mar. 30, 2016; 88 FR 16547, Mar. 20, 2023; 88 FR 27698, May 3, 2023; 88 FR 55563, Aug. 16, 2023]