Pharmacological and residue studies of two long acting oxytetracycline formulations injected subcutaneously in chickens and turkeys
Ziv, G.; Risenberg, R.; Weisman, Y.; Orgad, U.
Israel Journal of Veterinary Medicine 44(2): 139-140
ISSN/ISBN: 0334-9152 Accession: 001908058 Two long acting oxytetracycline (OTC) formulations Liquamycin LA-200 (Pfizer, U.S.A.) containing 200 mg OTC HCl/ml, and Engemycin-10% (Gist-Brocades, The Netherlands) containing 100 mg OTC HCl/ml were injected into the neck at 150 mg OTC HCl/kg to groups (8-10 birds/group) of chickens and turkeys. Serum OTC concentrations were determined at various times after treatment. Mean peak serum OTC concentrations (Cmax) in turkeys after injection of Liquamycin LA-200 and Engemycin-10% were 14.0 micro g/ml and 15.8 micro g/ml, respectively; differences were not significant at the 95% confidence level. In chickens, however, equal doses of the 2 formulations produced significantly lower Cmax values than in turkeys, i.e. 6.5 micro g/ml for both formulations. Serum OTC concentrations considered to be of potential therapeutic value, 1.0 micro g/ml, were maintained in turkeys and chickens for 72 h and approximately 60 h, respectively after treatment with Liquamycin LA-200 but for less than 48 h after treatment with Engemycin-10%. The turkeys appeared to be depressed 2-6 h after treatment with both formulations. Necrotic nodules were found near the injection site of 2 turkeys killed 3 weeks after treatment with Liquamycin LA-200. Concentrations of OTC in the necrotic material recovered from the injection site were 6.5 micro g/g and 4.0 micro g/g but drug residues were not found in any other body tissue. Histologically, several necrotic foci were found in the s/c fatty layer of the skin; these were surrounded by round cells and a few heterophilic granulocytes. Gross macroscopical changes at the injection site were not found in either of the 2 turkeys killed 3 weeks after treatment with Engemycin-10%. A single s/c injection of OTC in the form of Liquamycin LA-200 was capable of maintaining therapeutic serum drug levels for 2-3 days, but its use was associated with marked tissue damage at the injection site and may produce drug residue problems at marketing time. A similar drug dosing procedure using Engemycin-10%, although free of undesirable side-effects, failed to maintain for 48 h serum drug concentrations 1.0 micro g/ml.