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PMF 005-321 - Effectiveness Letter

PMF 5321 C-0004

Meg Oeller, D.V.M.
FDA Liaison to NRSP-7
Center for Veterinary Medicine
7500 Standish Place
Rockville, Maryland 20855

Dear Dr. Oeller:

We refer to your submission dated December 31, 1997, concerning the public master file (PMF) 5321 for the use of oxytetracycline hydrochloride (OTC) in sheep for the treatment of bacterial pneumonia caused by Pasteurella spp. Your submission contains the technical report of a study entitled “Pharmacokinetics of the long acting oxytetracycline Liquamycin LA-200Ò after a single intramuscular administration of 9 mg oxytetracycline/lb body weight to sheep and calves” to complete the effectiveness section of this PMF to support a new animal drug application (NADA) for this claim. It also contains a freedom of information (FOI) summary for effectiveness.

We have reviewed the submission and have the following comments.

  1. Given the slightly greater bioavailability observed in sheep than cattle, the similarity in the pathogens associated with the infection across the target animal species (Pasteurella multocida and Pasteurella haemolytica), the comparable in vitro pathogen sensitivity to the drug, and the similarity in disease syndrome for the two species, we conclude that Liquamycin LA-200Ò will be equally effective in the treatment of respiratory infections of sheep and cattle. Accordingly, the effectiveness technical section is complete to support an NADA for OTC use in sheep.
  2. Despite a high level of stability of drug concentrations in muscle and liver samples, OTC concentrations degraded over time in kidney and fat samples. Since this is a human food safety issue, this point (along with data showing a very large difference in estimated OTC concentrations when muscle, fat, or kidney samples are assayed using an HPLC versus a microbiological procedure) was forwarded to the Division of Human Food Safety (HFV-150).
  3. Considering the potential errors associated with the current OTC assay, the parameter estimates you obtained when modeling the current dataset are determined to be of questionable reliability. Nevertheless, the data are adequate to assess whether or not markedly higher or lower drug concentrations can be expected when Liquamycin LA-200Ò is administered to sheep versus cattle. This relative bioavailability assessment, which depends solely upon area under the curve (AUC) measurements and peak OTC concentrations (CMAX), provides the basis of our efficacy determination.
  4. We have revised the draft FOI summary and have provided a copy as an enclosure.

Future correspondence regarding this submission to the file for your PMF should be identified by the date of this correspondence and our file number, PMF 5321 C-0004, and be submitted to the Document Control Unit, HFV-199, Please include only one request per submission, clearly stating the request in the first paragraph.

If you have any questions regarding this submission, please contact Dr. William Flynn, Leader, Antimicrobial Drugs Team, at 301-827-7570.

Sincerely yours,

/s/
George K. Haibel, D.V.M.
Director, Division of Therapeutic Drugs
for Food Animals
Center for Veterinary Medicine
Office of New Animal Drug Evaluation

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