Skip to main content

CalfSpan* Tablets (Canada)

This page contains information on CalfSpan* Tablets for veterinary use.
The information provided typically includes the following:
  • CalfSpan* Tablets Indications
  • Warnings and cautions for CalfSpan* Tablets
  • Direction and dosage information for CalfSpan* Tablets

CalfSpan* Tablets

This treatment applies to the following species:
Company: Zoetis

Sustained - Release Sulfamethazine

DIN 01908375

Veterinary Use Only


50 tablets

MEDICINAL INGREDIENT: Each CalfSpan Tablet contains 8 grams of sulfamethazine in two distinct layers. The white layer provides sulfamethazine in a readily available form while the gray layer provides a slow-release form of the same drug.

ACTION: It is well established that the action of the sulfonamides as a group is one of bacteriostasis with high concentrations being bactericidal.1-5 The most commonly accepted theory of this antibacterial action is that the sulfonamide interferes with the normal metabolism of the bacterial cell, more specifically interfering with the utilization of para-aminobenzoic acid (PABA) in the bacterial enzyme system.1-5

Successful therapy with the sulfonamides depends heavily upon its proper usage. First, of course, the causative organism must be susceptible to this class of drugs.

Organisms susceptible to sulfonamides include certain Gram-positive cocci and diplococci, Gram-negative diplococci, and gram-negative bacilli. They are not effective in most viral and rickettsial infections or tuberculosis.2 Group A streptococci, some strains of staphylococci, Escherichia coli, Bacillus anthracis, diplococci, Pasteurella, Shigella, Vibrio, and Haemophilus are highly susceptible while Streptococcus viridans, Klebsiella, Aerobacter, B. proteus, Pseudomonas, clostridia, P. tularensis and Brucella are only moderately susceptible. Psittacosis (ornithosis) and actinomycosis may respond to sulfonamide therapy though most viruses and fungi are highly resistant to this group of drugs.2

Beyond this, it is extremely important to:

1. Give the drug early in the course of the disease.

2. Give adequate dosage.

3. Continue medication for a short time after the temperature is normal, to give body defenses a chance to eliminate the infecting organism.

Proper case selection and early administration of a sufficient dose are less difficult to achieve in clinical veterinary practice than is the continuation of drug dosage for an adequate length of time. Jones states that “Animals difficult to restrain may receive no more than one or two doses.”4

Historically sulfonamide therapy dates back to the 1930s. Scores of related compounds with varying degrees of solubility, toxicity, and duration of activity have evolved. In order to maintain adequate blood levels with the earlier compounds of this group, it was necessary to administer the drug at very frequent intervals.

In more recent years, however, sulfonamides have been synthesized which are capable of producing therapeutic blood levels that are sustained for 24 hours. Sulfamethazine is outstanding among this group. Daily administration, however, was still necessary for 3 or 4 days if therapeutic levels of sufficient duration were to be achieved.

SUSTAINED ACTION: CalfSpan Tablets combine sulfamethazine in a single tablet of 2 distinct layers. The smaller white layer provides sulfamethazine in a readily available form while the larger gray layer provides a slow-release form of the same drug. Studies with these tablets showed that following a single oral dose at the rate of 1 tablet per 45 lb (20 kg) of body weight, plasma sulfamethazine levels of 5 mg/dl generally occurred within 6-24 hours after treatment. Plasma levels of 5 mg/dl or higher extended to at least the fourth day post treatment. These in vivo studies were conducted in calves ranging in weight from approximately 75 lb (34 kg) to approximately 150 lb (68 kg). Bacterial pathogens are thus exposed to sustained levels of sulfamethazine for a period of time sufficient to allow body elimination of those which are sensitive to the drug.

CalfSpan* Tablets Indications

CalfSpan Tablets are recommended for the treatment of infectious diseases of calves in which the causative organism is susceptible to sulfamethazine. Uses include the following:

1. Colibacillosis (bacterial scours) (E. coli).

2. Bacterial pneumonia (Pasteurella spp.)

3. Calf diphtheria (Fusobacterium necrophorum).

4. Treatment of bovine respiratory disease complex (shipping fever complex) (Pasteurella spp.)

5. An aid in the treatment of necrotic pododermatitis (foot rot) (Fusobacterium necrophorum).

Dosage and Administration

To reduce the development of antimicrobial resistance and maintain effectiveness, use this antibiotic prudently and for the shortest duration required to achieve the desired clinical outcome.

Administration as a single oral dose at the rate of 1 CalfSpan Tablet for each 45 lb (20 kg) of body weight. If no response is evident within 2-3 days, other therapeutic approaches should be considered. Tablets may be halved if necessary to closely approximate dosage requirement, but do not crush.

Administration of CalfSpan Tablets early in the course of the infection is imperative for best results. A single dose will provide adequate blood sulfonamide levels that will be sustained for at least 4 days.

CAUTIONS: Reports of side effects following the use of sulfamethazine in cattle are rare. Renal damage may result from crystallization of the drug in the kidneys. If hematuria develops during CalfSpan Tablet therapy, take measures to increase the fluid intake of the animal.

Care should be taken to ascertain that the tablets are swallowed before the animal is released. As with any orally administered tablet, occasional regurgitation will occur in ruminants.

TISSUE RESIDUE: Since CalfSpan Tablets provide sustained release of the active ingredient, tissue levels of sulfamethazine remain for a longer period of time than when this drug is administered in conventional forms. Tissues examined 28 days after treatment showed no residual sulfonamide levels in excess of 0.1 ppm. From samplings at earlier times, levels in excess of 0.1 ppm were shown.


Treated animals must not be slaughtered for use in food for at least 28 days after the latest treatment with this drug. Not for use in lactating dairy animals. Sulfonamides can cause allergic reactions in sensitized individuals. When handling the product, avoid inhalation, oral exposure and direct contact with skin or eyes. Keep out reach of children.


Store at a temperature between 15 and 30° C.


1. Davison FM: Synopsis of Materia Medica, Toxicology and Pharmacology. The C.V. Mosby Company, Third Edition, 1944.

2. Drill’s Pharmacology in Medicine. Edited by Joseph R. DiPalma, McGraw-Hill, Third Edition, 1965.

3. Goodman LS, Gilman A: The Pharmacological Basis of Therapeutics. The MacMillan Company, Third Edition, 1969.

4. Meyer JL: Veterinary Pharmacology and Therapeutics. The Iowa State College Press, Second Edition, 1957.

5. Sollman TA: Manual of Pharmacology. W.B. Saunders Company, Sixth Edition, 1944.

*Zoetis and CalfSpan Tablets are trademarks of Zoetis or its licensors, used under license by Zoetis Canada Inc.

Manufactured by: Can-Vet Animal Health Supplies Ltd., 4-61 Malcolm Rd., Guelph, ON N1K 1A7


Distributed by: Zoetis Canada Inc., Kirkland QC H9H 4M7




CPN: 1198017.5

Order Desk:   800-663-8888
Technical Services Canada:   800-461-0917
Technical Services USA:   800-366-5288
THIS SERVICE AND DATA ARE PROVIDED "AS IS". Animalytix assumes no liability, and each user assumes full risk, responsibility, and liability, related to its use of the Animalytix service and data. See the Terms of Use for further details.

Copyright © 2023 Animalytix LLC. Updated: 2023-11-27