November 29, 2018

Dear Animal Drug Sponsor:

During FDA’s Public Meeting on Antiparasitic Drug Use and Resistance in Ruminants and Equines, held by CVM on March 5th and 6th, 2012, a panel of veterinary parasitology experts participated in an extensive discussion on anthelmintic resistance in the United States and around the world. During that discussion, the panel agreed that, in general, end users of these products were not aware of the emergence of anthelmintic drug resistance in parasites of grazing species in the U.S. The panel also agreed that end users were not adequately informed regarding antiparasitic resistance development, and appropriate drug use and management practices. After considering the information from this meeting and other sources, FDA is recommending that consistent statements be added to the labeling of anthelmintic drugs for grazing animals to help end users better understand how the appropriate use of these drugs may slow the development of anthelmintic resistance.

More specifically, FDA is recommending that the labeling of all anthelmintics for grazing animals (cattle, sheep, goats, horses) include the following statements:

1. Under a section titled “Other Warnings”:

• Parasite resistance may develop to any dewormer, and has been reported for most classes of dewormers.
• Treatment with a dewormer used in conjunction with parasite management practices appropriate to the geographic area and the animal(s) to be treated may slow the development of parasite resistance.
• Fecal examinations or other diagnostic tests and parasite management history should be used to determine if the product is appropriate for the herd/flock, prior to the use of any dewormer. Following the use of any dewormer, effectiveness of treatment should be monitored (for example, with the use of a fecal egg count reduction test or another appropriate method).
• A decrease in a drug’s effectiveness over time as calculated by fecal egg count reduction tests may indicate the development of resistance to the dewormer administered. Your parasite management plan should be adjusted accordingly based on regular monitoring.

2. Under the section “Dosage and Administration,” or similar section of the labeling that describes the dosing of the product:

• Do not underdose. Ensure each animal receives a complete dose based on a current body weight. Underdosing may result in ineffective treatment, and encourage the development of parasite resistance.

Although the majority of swine and poultry in the US are not raised similarly to cattle, small ruminants, and horses, a growing number of swine and poultry are being raised on or otherwise have access to pastures. This increases their exposure to parasites and the accompanying risk of anthelmintic resistance in those parasites. Therefore, the FDA is recommending consistent statements be added to anthelmintics for these species as well. Because parasite management in swine and poultry differ from that of traditional grazing species, the statements recommended for these products reflect those differences.

FDA is recommending that the labeling for all anthelmintics for swine and poultry include the following statement under a section titled “Other Warnings”:

• Parasite resistance may develop to any dewormer. All dewormers require accurate dosing for best results. Following the use of any dewormer, effectiveness of treatment should be monitored. A decrease of effectiveness over time may indicate the development of resistance to the dewormer administered. The parasite management plan should be adjusted accordingly based on regular monitoring.

Finally, because the use of extended-release macrocyclic lactone anthelmintic products may increase selection pressure for resistant parasites, FDA is recommending that the labeling of these products include the following additional statement under a section titled “Other Warnings”:

• Macrocyclic lactones provide prolonged drug exposure that may increase selection pressure for resistant parasites. This effect may be more pronounced in extended-release formulations.

Through this letter, FDA requests that all sponsors of approved anthelmintics used in grazing animals (cattle, sheep, goats, horses) and in swine and poultry add the above statements as appropriate for each specific product. The continued availability of effective anthelmintics is important for animal health. Therefore, it is in the interest of animal health to take a more proactive approach to assure that anthelmintics are used appropriately to help maintain the effectiveness of these drugs.

Our records indicate that you are the sponsor of one or more new animal drug applications (NADAs) or abbreviated new animal drug applications (ANADAs) for drug products or combination drug products that are subject to this request. A listing of the applications FDA has identified as being subject to this request is attached to this letter. These labeling revisions may also pertain to other NADAs or ANADAs that you own that are not listed in the attachment. If you are the sponsor of additional NADAs or ANADAs anthelmintics approved for use in sheep, goats, cattle, horses, swine, and/or poultry, please contact us to discuss potential changes in labeling for those products. For products not currently marketed, we ask that you provide us a letter stating your commitment to revise the product labeling before you resume marketing. You should submit this letter to the Drug Experience Report (DER) under form FDA 2301.

FDA requests that sponsors of NADAs for anthelmintics approved for use in grazing animals (cattle, sheep, goats, horses), swine or poultry submit a supplemental application that includes labeling revisions within twelve (12) months from the date of this letter or at the next label printing, whichever comes first.

FDA will work with sponsors of combination medicated feed NADAs and ANADAs covered by this request, to expeditiously align their applications with the revised labeling of the relevant pioneer NADA (i.e., individually approved Type A medicated article for combination medicated feed NADAs; and reference listed new animal drug for ANADAs), once the reference NADA supplemental application has been approved.

We encourage you to contact the Office of New Animal Drug Evaluation (ONADE) Project Management Team to discuss general strategy plans for your portfolio of affected applications. If you do not have a Project Manager assigned to you, please contact Aila Albrecht, PMP, by telephone: 240-402-0625 or email: aila.albrecht@fda.hhs.gov. If you own only generic products, please contact Sharon Ricciardo, by telephone: 240-402-0854 or email: Sharon.ricciardo@fda.hhs.gov.
When you are ready to submit your supplemental labeling applications, please direct them to the appropriate division within ONADE:

• Submit supplemental applications for pioneer (NADA) products for use in horses to the Division of Therapeutic Drugs for Non-Food Animals (HFV-110);
• Submit supplemental applications for pioneer (NADA) products for use in cattle, sheep, goats, swine, and/or poultry to the Division of Therapeutic Drugs for Food Animals (HFV-130);
• Submit supplemental applications for pioneer (NADA) products for use in food animals AND horses to the Division of Therapeutic Drugs for Food Animals (HFV-130);
• Submit supplemental applications for pioneer (NADA) medicated feed combinations to the Division of Production Drugs (HFV-120);
• Submit supplemental applications for generic (ANADA) products to the Division of Generic Animal Drugs (HFV-170).

Sincerely,

Dr. Neal Bataller, Director
Division of Surveillance (HFV-210)
FDA/Center for Veterinary Medicine
7519 Standish Pl. Rockville, MD 20855