This is the only published info I have found:
http://www.ncbi.nlm.nih.gov/pubmed/24853528
J Food Prot. 2014 Jun;77(6):1017-21. doi: 10.4315/0362-028X.JFP-13-440.
Withdrawal times of oxytetracycline and tylosin in eggs
of laying hens after oral administration.
Muñoz R1,
Cornejo J2,
Maddaleno A1,
Araya-Jordán C1,
Iragüen D1,
Pizarro N1,
San Martín B3.
Author information
Abstract
Antimicrobials administered to laying hens may be distributed into egg white or yolk, indicating the
importance of evaluating withdrawal times (WDTs) of the pharmaceutical formulations. In the present
study, oxytetracycline and tylosin's WDTs were estimated. The concentration and depletion of these
molecules in eggs were linked to their pharmacokinetic and physicochemical properties.
Twenty-seven Leghorn hens were used: 12 treated with oxytetracycline, 12 treated with tylosin,
and 3 remained as an untreated control group. After completion of therapies, eggs were collected
daily and drug concentrations in egg white and yolk were assessed. The yolk was used as the target
tissue to evaluate the WDT; the results were 9 and 3 days for oxytetracycline and tylosin,
respectively. In particular, oxytetracycline has a good oral bioavailability, a moderate apparent
volume of distribution, a molecular weight of 460 g/mol, and is lightly liposoluble. Tylosin, a
hydrosoluble compound, with a molecular weight of 916 g/mol, has a low oral bioavailability and a
low apparent volume of distribution, too.
Present results suggest that the WDTs of the studied
antimicrobials are strongly influenced by their oral bioavailability, the distribution, and the molecular
weight and solubility, and that these properties also influence the distribution between the egg yolk
and white.
PMID:
24853528
[PubMed - indexed for MEDLINE]
