Desmethyl-danofloxacin

After oral administration of radiolabeled danofloxacin to chickens or intramuscular administration to cattle, residues of total residues in all tissues declined rapidly with time. In both species, total residues were highest in liver at all time points. Unmetabolized danofloxacin was the major component in chicken liver and constituted 47-61% of total residues at 6-24 h after treatment. Residues of A-desmethyl danofloxacin over the same period were 14-20% of the total liver residues. Residues in cattle consisted of 14-32% danofloxacin. Residues of N-desmethyl danofloxacin declined from 30-40% of the total residues at 12 h to 14% at 72 h. 

The metabolism of danofloxacin does not differ in swine. When five daily intramuscular injections of 1.25 mg radiolabeled danofloxacin/kg bw were given to pigs, the parent drug accounted for 72-81 % of the radioactivity excreted in feces and urine over the 5- day dosing period (143). In feces, 5-7% of the radioactivity was identified as A-desmethyl danofloxacin. In urine, 2-3% was A-desmethyl danofloxacin, 10-14% danofloxacin-A-oxide, and 3% danofloxacin glucuronide. 

Residue depletion studies in chickens showed that residues of danofloxacin in muscle declined from 36-90 ppb at 6 h to less than 25 ppb at 18 h after withdrawal of treatment. Residues of the A-desmethyl metabolite were less than 25 ppb at all time points. Residues of danofloxacin in liver declined from 157-319 ppb at 6 h to 18-66 ppb at 36 h after withdrawal of treatment. Residues of the A-desmethyl metabolite were 35-193 ppb and less than 10 ppb over the same time points. 

The following QUINs and FQUINs could be analyzed pipemedic acid (PIP), enoxacin (ENO), norfloxacin (NOR), ciprofloxacin (CIPRO), lomefloxacin (LOME), desmethyl-danoflox-acin (DES), danofloxacin (DAN), enrofloxacin (ENRO), sarafloxacin (SARA), cinoxacin (CINO), oxolinic acid (OXO), nalidixic acid (NALA), flumequin (FLU), piromidic acid (PIRA), marbo-floxacin (MAR), difloxacin (DIFLX), decoquinate (DEC), and ofloxacin (OFLX). 

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