Stability 
Chlortetracycline is unstable in body fluids and as much as 88 percent may be 
inactivated in 1 hour when exposed to serum in vitro (5,7). The fact that urinary excre- 
tion may occur for 70 hours after the last dose indicates that in vivo deterioration must 
be somewhat less rapid than would be expected from the in vitro results. Oxytetracycline 
is stable in the presence of various body fluids in vitro. The stability of others has been 
discussed in the text. 
The antibiotics that are used most frequently in animals have been shown to be 
stable or not inactivated by their passage throughthe G.I. tract; however, chloramphenicol 
is destroyed or inactivated in the tract. Their stability in feces after voiding is not known. 
Effect of cooking meat containing cycline antibiotics: Theaverage amount of cooking 
destroys the chlortetracycline that is found in chicken meat resulting from feeding high 
levels of antibiotic. Cooking also destroys all or practically all the cycline antibiotic 
residue in meat after post slaughter treatment which has been used as an aid in preser- 
vation, 
REFERENCES 
1. E, Jawotz. Polymixin, Neomycin, Bacitracin. 96 pp. Medical Encyclopedia Inc., 
New 19562 
2. M. H. Lepper. Aureomycin (chlortetracycline). 156 pp. Medical Encyclopedia Inc., 
Neate L950. 
3. M. M. Musselman, Terramycin (oxytetrocyline), Medical Encyclopedia Inc., N. Y. 
1956. 
4. S.A. Waksman, Neomycin. Rutgers Univ. Press. 1953. 
5. H. Welch, et al. Principles and practice of antibiotic therapy. 699 pp. Medical 
Encyclopedia Inc, 1954, 
6. J. M. Pensack, C. N. Huhtanen, and E. L.R. Stokstad. Laboratory evaluation of 
methods for potentiating antibiotics. Am. Cyanamid Co, 10th Animal Feed Sym- 
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7. R.G. Brown and H. S. Bachman. Physiology and pharmacology of the potentiation of 
aureomycin. Ibid. pp. 93-104. 
8. J. S. Kiser. Increasing the effectiveness of antibiotics as chemotherapeutic agents. 
Ibid. pp. 5-14. 1959. 
9. R. E. Eggert and R. F. Elliot. The potentiation of Aureomycin in swine. Ibid. pp. 
65-92, 1959. J. An. Sci. 18: 1505-1959. 
10. K. E. Price, Z. Zolli, J. C. Atkinson, A. P. Collins, and H. G. Luther. Antibiotic 
inhibitors III, Reversal of calcium inhibition of intestinal absorption of oxytetra- 
cycline in chickens by certain acids and acid salts, Antibiotics Annual 1958- 
59: 1020-32. 
11. G. Van Helsema, et al. The importance of using more than one animal species for 
blood level determination. Antibiotics Ann. 1955-59: 418. 
12. L. L. Rusoff, H. H. Hester, Jr., and F, L. Landagore. Concentration of chlortetra- 
cycline in the body of dairy calves receiving nutritional levels of the antibiotic. 
Antibiotic Ann. 1954-55: 348. J. Dairy Science 37:488. 1954. 
13. P. B. English. Serum penicillin concentrations inthe bovine with fortified benzathine. 
Austral, Vet. Je35:3535 1959; 
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