Code of Federal Regulations Title 21. Food and Drugs § 21.520.2280 Sulfamethizole and methenamine

(1) Amount. Administer orally 1 tablet per 20 pounds of body weight 3 times per day until clinical signs are alleviated. To reduce the possibility of relapse, continue therapy for a week to 10 days.

(2) Indications for use. For treatment of urinary tract infections such as cystitis, nephritis, prostatitis, urethritis, and pyelonephritis. As an aid in the management of complications resulting from surgical manipulations of the urinary tract such as removal of calculi from the bladder, in ureterostomies, and in instrumentation of the urethra and bladder.

(3) Limitations. Federal law restricts this drug to use by or on the order of a licensed veterinarian.