Pharmacokinetic and Metabolic Profile of Difloxacin in Camels Following Parenteral Administration

摘要

The pharmacokinetics of difloxacin delivered by both Intravenous (IV) and Subcutaneous (SC) routes and its metabolic profile and elimination pattern following the subcutaneous administration of 5 mg kg-1 were investigated in a crossover study using 10 camels (Camelus dromedaries). Multiple plasma, faecal and urine samples were collected for the quantitation of difloxacin and its metabolites using HPLC with fluorescence detection and mass spectrometry for the elucidation of metabolite structure. Difloxacin was eliminated from plasma with elimination half-lives of 6.65 and 7.52 h following Intravenous (IV) and Subcutaneous (SC) administration, respectively. The drug was absorbed slowly following SC administration and a maximum concentration of 2.1 μg mL-1 was attained at (Tmax) 4 h with a bioavailability of 94.6%. Difloxacin was metabolised in camels by the N-demethylation pathway to produce the active metabolite sarafloxacin (M1) and by oxidation into three other metabolites, 3-oxosarafloxacin (M2), 3-oxodifloxacin (M3) and desethylenesarafloxacin (M4). The concentrations of the circulating Metabolites in plasma (M1, M2 and M3) were much lower than that of the parent drug. The administered dose of difloxacin was eliminated largely in its parent form in faeces (69.5%) and to a small extent in urine (5.9%) whereas sarafloxacin (M1) and 3-oxosarafloxacin (M2) were the main metabolites detected in faeces (7.2 and 3%) and urine (3.5 and 1.8%). The other metabolites, 3-oxodifloxacin (M3) and desethylenesarafloxacin (M4) were detected to a minimal extent in faeces only and amounted to 1.47 and 0.6% of the dose, respectively. The results of the present study revealed that the N-demethylation and oxidative pathways of biotransformation are the primary routes of difloxacin metabolism in camels with renal and hepatobiliary excretion through urine and faeces. Phase II conjugation plays a minor role in the elimination of the drug in camels.