Metabolism And Pharmacokinetics Of Cyadox In Dogs And Cats Following Oral,Intramuscular And Intravenous Administration

Quinoxaline 1,4-di-N-oxide(QdNO)derivatives have been used worldwide to promote the growth and to treat several bacterial infections in animals since 1970 due to the potent antibacterial activity of these synthetic antibacterial agents.The wellknown members of this group,such as olaquindox,mequindox and carbadox have been banned or strictly limited to use due to their potential toxicities in animals.Cyadox(Cyx),2-formylquinoxaline-N1,N4-dioxide cyanocetylhydrazone,is a novel derivative of QdNOs and a promising antibacterial agent believed to be safer for use as compared to its congeners due to the structural modification.It has been characterized as an effective broad-spectrum antibacterial agent against the majority of pathogenic bacteria(including Staphylococcus,Pasturella and Salmonella spps)in animals and has stronger effect in anaerobic condition.Cyx has been developed as the drug of choice to prevent Escherichia coli infection in pigs and chickens owing to its good activity and lack of toxic effects.Dogs and cats are generally more prone to these types of bacterial infections.Therefore,Cyx might be a promising agent to treat the bacterial infections of canine and feline species because of the safety demonstrated in the previous work.During drug development process,accurate assessment of metabolism as well as pharmacokinetics and affecting factors are very important for the evaluation of the safety and effectiveness,and also for rational treatment design.In this work,the metabolism and pharmacokinetics of Cyx in beagle dogs and domesticated cats following oral(PO),intramuscular(IM)and intravenous(IV)administration were studied to explore the difference of metabolism and pharmacokinetic profiles through different routes of administration and the possibility of its clinical use for treatment purpose.A high performance liquid chromatography with ultraviolet(HPCL-UV)detection best suited for identification and quantification of Cyx and its major metabolites was developed with good recovery and short time in plasma,feces and urine of dogs and cats for comprehensive assessment of pharmacokinetic and metabolism profiles.The recoveries of all five analytes in the plasma were > 80 % when used methanol(MeOH)as extracted solvent,whereas,in feces and urine,best recovery(> 70 %)was achieved by using 1 % metaphosphoric acid with the ratios of MeOH/Acetonitrile(ACN)/water(50:20:30,v/v/v)and 2 % metaphosphoric acid,respectively.The Oasis HLB was superior to other cartridges in terms of good recovery and low matrix interference.For elution step of Oasis HLB,MeOH was found to be the superlative choice.Regarding the chromatographic analysis,the best peak shapes were obtained with ACN and 0.5 % formic acid on a gradient elution mode with the wavelength set at 320 nm.The limit of detection(LOD)for plasma,urine and feces of dogs and cats were 0.02 ?g mL-1,0.1 ?g mL-1 and 0.1 ?g g-1,while limit of quantification(LOQ)were 0.05 ?g mL-1,0.2 ?g mL-1 and 0.2 ?g g-1,respectively.The linear range of standard calibration curves for plasma urine and feces were 0.02-10.24 ?g mL-1,0.1-6.4 ?g m L-1 and 0.1-6.4 ?g g-1,respectively.The correlation coefficient of standard calibration curves were above 0.999.Matrix effects of all analytes were not above 10 %,which are lower than other reports.Metabolism and pharmacokinetics of Cyx and its main metabolites in dogs and cats were determined through different routes of administration in a crossover design with 2 weeks of washout period.For PO delivery,a suspension(80 mg m L-1)was prepared by dissolving an appropriate amount of drug into 0.5 % sodium carboxymethyl cellulose aqueous solution and administered to 6 beagle dogs(3 males,3 females)and 6 domesticated cats(3 males,3 females)through oral gavage at a dose rate of 40 mg kg-1b.w.Blood(1 m L)was collected from the cephalic vein in heparincontaining tubes before and after different time points of PO administration.Urine and feces were collected in ice bags before and after 12 and 24 h,followed by intermittent collection from days 1 to 14 after each route of administration.The concentration vs.time profile in plasma after PO administration indicated that Cyx is rapidly dissociated into 1,4-bisdesoxycyadox(Cy1),Cyadox-1-monoxide(Cy2),N-(quinoxaline-2-methyl)-cyanide acetyl hydrazine(Cy4)and Quinoxaline-2-carboxylic acid(Cy6)and eliminated from plasma earlier compared to its metabolites.Total recovery of Cyx and its metabolites in dogs and cats were 64.51 and 59.09 %,respectively,in urine and feces,while feces were detected as major route of excretion.The area under curve(AUC)of cyadox in dog and cat were 1.22 and 0.863 h×?g m L-1,respectively,and the oral bioavailabilities were 4.75 and 4.37 %,respectively.The AUC and bioavailability of Cyx were lower as compared to its main metabolites.Mean resident time(MRT)of Cyx in dogs(7.32 h)and cats(5.92 h)were lower than Cy1,Cy2,Cy4 and Cy6.These results revealed that there may be first-pass effect of Cyx which makes this route suitable to treat intestinal infection.For IM and IV routes,a suitable suspension was made by recrystallization based on acid base neutralization and administered to 6 beagle dogs(3 males,3 females)and 6 domesticated cats(3 males,3 females)at a dose rate of 10 mg kg-1 b.w.1 mL blood was collected in heparin containing tubes before and after different time points after IM and IV injections from the both species.Following IM injection,total recovery in urine and feces was > 60 % in both species and urine was detected as major route of excretion with total recovery of 43.2 and 47.68 % in dogs and cats,respectively.In dogs and cats,AUC of Cyx was 6.3 and 4.12 h×?g mL-1 and MRT were 3.58 and 4.45 h,respectively,suggesting that Cyx eliminated from plasma earlier compared to its metabolites.Bioavailability of Cyx in dogs and cats were 97.28 and 84.43 %,respectively,suggesting this route as better choice for treatment of systemic infections.Following IV injection,total recovery of drug in urine and feces of dogs and cats were 62.48 and 63.72 % and urine was depicted as major excretory route with 45.37 and 48.08 % recovery,respectively.The MRT of Cyx was 0.556 and 0.389 h,whereas the AUC of Cyx was 6.66 and 5.09 h×?g m L-1 in dogs and cats,respectively.The results showed that Cyx eliminated from plasma quickly and dissociated into its metabolites.In conclusion,Cyx was comprehensively metabolized in dogs and less ability of glucuronidation in cats did not show any adverse impact on Cyx metabolism.Low bioavailability after PO administration makes this route better choice to treat the intestinal infection.However,high bioavailability after IM injection makes this route suitable to treat the systemic infections.These results provide comprehensive information for evaluation of Cyx through different routes of administration and improve the understanding of pharmacology which will help its judicious use in dogs and cats.