Comparative stability of oxytetracycline and tylosin in sugar syrup

Abstract - Measurements of OTC stability in apicultural dosage forms have relied on methods (fluorescence, bactericidal effects) that are not specific to OTC. We have measured the stability of OTC and tylosin in sucrose syrup using high-performance liquid chromatography. At 34 °C in the dark, OTC in syrup made from highly purified sucrose had a half life of 7.6 days. Tylosin was considerably more stable, with a half life of 186 days; the half life of the total tylosin complex was 287 days. In syrup prepared from commercial-grade sugar, both materials were less stable, with OTC having a half life of 6.3 days and tylosin about 75 days. Microbiological data paralleled these findings, with a rapid decrease of inhibition zone against Paenibacillus larvae with OTC, and a persistence of inhibition with tylosin. © Inra/DIB/AGIB/Elsevier, Paris