April 5, 1989

PMF 5206

Emilio E. Viera, D.V.M.
Division of Therapeutic Drugs
  for Food Animals - HFV-130
Center for Veterinary Medicine
Food and Drug Administration
5600 Fishers Lane
Rockville, MD 20857

Dear Dr. Viera:

Reference is made to your submission under Public Master File (PMF) 5206 dated March 3, 1989, as amended March 28, 1989, providing for the use of sulfamethazine sustained release in sheep for the treatment of bacterial pneumonia caused by Pasteurella spp. and colibacillosis caused by Escherichia coli. The submission contained the results of the projected plasma sulfamethazine levels in sheep which were calculated following administration of two doses of calf-span at 48 hour intervals at the recommended dosage for calves.

We have completed our review of the submission, and we agree with your findings that a therapeutic regimen in sheep of two doses (180 mg per pound body weight), administered at an interval of 48 hours will maintain blood levels of sulfamethazine consistent with CVM standard of 8 mg percent. Accordingly, the efficacy data are acceptable for the use of sustained released sulfonamide in sheep for the treatment of bacterial pneumonia caused by Pasteurella spp. and colibacillosis caused by Escherichia coli.

Sincerely yours,

/s/
Donald A. Gable, D.V.M.
Director, Division of Therapeutic
  Drugs for Food Animals
New Animal Drug Evaluation
Center for Veterinary Medicine