Drug Use Clarification Act (AMDUCA) of 1994. Prior to AMDUCA, veterinarians were not legally permitted to use an animal drug in any way except as indicated on the label. Following the passage of AMDUCA, veterinarians gained the right to prescribe/dispense the “extralabel” use of drugs but the Food and Drug Administration (FDA) places limits the extralabel use of drugs to protect public health.
Extralabel drug use [ELDU] occurs when the drug’s actual or intended use is in a manner not in accordance with the approved labeling. For instance, ELDU occurs when administration is:

Dr. David Smith Associate Professor Veterinary and Biomedical Sciences, University of Nebraska

• for a species not listed on the label;
  
• for an indication, disease or other condition, not on the label;
  
• is at a dosage level or frequency not on the label; or
  
• by a route of administration not on the label.

The ELDU rule allows veterinarians legally to go beyond label directions in using animal drugs, and permits them to use legally obtained human drugs in animals. However, the rule does not permit ELDU in animal feed. Further, ELDU must take place within the confines of a valid veterinarian-client-patient relationship. This means that the veterinarian must have sufficient knowledge of the animal to make a preliminary diagnosis on which the intended use of drugs is based. In the case of food producing animals, the veterinarian is responsible for establishing a “substantially extended withdrawal time” that is “supported by appropriate scientific information.” This latter requirement is one that FARAD is especially geared up to help practitioners meet.

ELDU is limited to cases in which the health of the animal is threatened, or suffering or death may result from a lack of treatment. ELDU is not an option where the drug use is to enhance production. Veterinarians can consider ELDU in food-producing animals only when no approved drug is available for use that contains the same active ingredient in the required dosage form and concentration, or that the veterinarian finds that there is no approved drug that is clinically effective for the intended use.

In summary, the veterinarian must:

• Make a careful diagnosis or evaluation of the conditions to be treated;
  
• Establish a substantially extended drug withdrawal period that is supported by scientific evidence;
  
• Take the steps necessary to be sure the withdrawal period is met and no illegal drug residues occur in food from the treated animals; and
• Institute procedures to make sure the treated animal’s identity is known. And that records relating to details of the ELDU are retained for the required two years.

The AMDUCA regulation places requirements on the veterinarian to properly label the drugs used extralabel and to give the livestock owner complete instructions about proper use of the drug and withdrawal times. Veterinarians remain responsible for any voliative drug tissue residues that occur because of ELDU under their supervision.

Under no circumstances can a non-veterinarian order the extralabel use of a drug in animals. This is the reason that FARAD’s consultative services have to be limited to veterinarians.

Prohibited from extralabel use

AMDUCA also gives FDA the right to prohibit the use of certain drugs from use in food producing animals when their use can be a hazard to human health.

The prohibition can be against all uses of a drug, or against the use in limited species, or limit use to certain indications, dosages, forms, routes of administration, or a combination of factors. The list currently includes:

• Chloramphenicol
  
• Clenbuterol
  
• Diethylstilbestrol
  
• Dimetridazole and Other nitroimidazoles (including metronidazole)
  
• Furazolidone, nitrofurazone, other nitro furans (including topical administration)
  
• Fluoroquinolones
  
• Glycopeptide
  
• Ipronidazole
  
• Gentian Violet
  
• Phenylbutazone animal and human drugs in female dairy cattle 20 months of age or older
  
• Sulfonamide drugs in lactating dairy cattle (except approved use of sulfadimethozine, sulfabromomethazine, and sulfaethoxpyridazine

There were two new prohibitions added last year. They were for drugs used to treat influenza in humans. These drugs, or classes of drugs, are prohibited from use in chickens, turkeys, and ducks:

• Adamantanes (amantadine and rimantadine)
  
• Neuraminidase inhibitors (oseltamivir and zanamivir)

February 2007