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B. SULFANOMIDES:

Because, of the potential for sulfonamides to cause milk residues. The
FDA stated position to the veterinary profession and dairy industry, is, it is
not acceptable to use any sulfonamide, except the three
sulfonamides approved for use in lactating dairy cattle, to treat
female dairy cattle 20 months of age or older.

 Sulfamethazine:

There are approved products that contain sulfamethazine (SMZ) for use in
young cattle. The approved products contain only SMZ and carry this or
similar statement,

"WARNING: Do not use in female dairy cattle 20 months of age or
older. Do not use in calves under one month of age or calves fed an
all milk diet."

These approved products may be used on animals less than 20 months
of age and stored with the non-lactating drugs.

 Other Sulfonamides, 510.450 Sulfonamides, and Combination Prod-
ucts

FDA has taken steps with respect to sulfonamide products marketed under
21CFR 510.450. This regulation provided for the marketing of sulfonamide
products on an interim basis, pending the resolution of safety concerns.
Based on scientific information, showing that the degree of thyroid
response to sulfonamide exposure should be given greater significance in
the evaluation of toxicity, FDA declared all sulfonamide drugs to be new
animal drugs requiring approval. Sponsors of sulfonamide drugs were
required to submit new animal drug applications containing toxicity studies.

The final rule revoking 21CFR 510.450 was published in the Federal
Register August 9, 1990. All unapproved sulfonamide drugs are subject to
regulatory action.

Rarely, supplies of these products may be encountered in drug distribution
facilities and on dairy farms. Some products' labels bear indications for

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