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U.S. Department of Health and Human Services

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M-I-98-8: Tetracycline Test Method

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TO: All Regional Food and Drug Directors
Attn: Regional Milk Specialists

FROM: Milk Safety Branch

SUBJECT: Tetracycline Test Method

The Center for Veterinary Medicine has completed the evaluation of the data submitted to support the modification of the Charm II Tetracycline Drug Test (Competitive), to detect tetracycline residues at or below their new tolerances in raw milk. FDA has determined this test meets the standards established for acceptance of screening tests labeled for detecting drug residues in raw milk.

Following the approval of Liquamycin LA-200 (oxytetracycline) for use in lactating dairy cattle on July 21, 1998, a new tolerance of 300 ppb was established for the sum of residues of tetracyclines in milk. With this new tolerance, a tolerance of 300 ppb for each of the three tetracyclines (chlortetracycline, oxytetracycline and tetracycline) was also established.

The data provided by Charm Sciences supports the use of the current test with the additional requirement that the milk sample be diluted 1:10 with the Charm zero control standard which will be provided as a component of the test. Only the diluent provided with the Charm II Tetracycline Drug Test (Competitive) may be used to for this dilution. Charm Sciences has agreed to revise the labeling of this test to reflect this modification and the new 90/95 percent detection levels and drug concentration responses.

The 1:10 dilution must be performed prior to beginning this test for tetracycline residues. Milk should not be screened, rejected or accepted using this test with undiluted samples.

The 90/95 percent detection levels and the drug concentration responses for the three tetracyclines are:

Table 1 - 90/95 PERCENT DETECTION LEVELS (ppb)

DRUG

90/95 % Detection Levels (ppb)

Chlortetracycline

257

Oxytetracycline

119

Tetracycline

67

 

Table 2 - DRUG CONCENTRATION RESPONSES

Drug Concentration (ppb) Chlortetracycline Oxytetracycline Tetracycline

20

   

0

30

   

7

40

   

37

60

 

13

93

70

 

37

 

90

17

   

100

 

87

 

120

20

   

150

 

100

 

160

77

   

230

93

   

300

97

100

100

 

Copies of this memorandum are enclosed for your distribution to District Milk Specialists, state milk regulatory agencies, State Laboratory Evaluation Officers and State Milk Rating Officers in your region. This memorandum is also available on the FDA Prime Connection Computer bulletin board system, and should be widely distributed to representatives of the milk industry, state veterinarians, state veterinary and pharmacy boards, veterinarian professional organizations, and all other interested parties.

 

Signature,

Joseph M. Smucker, Chief
Milk Safety Branch