INTRODUCTIONIt is well recognized that oral drug administration might notbe suitable for ruminants, because of long residence of drugs inrumen or slow drug absorption. Since slow absorption does notalways result in longTmax,there are drugs for which an oralroute is appropriate even in ruminants. We previously found arapid antipyretic effect of diclofenac (DF) in dairy cows withinfectious disease following its oral administration in a preli-minary trial. We also reported that DF which have high lipo-phylicity may be substantially absorbed from the forestomachof goats (Elbadawyet al., 2015). In this study, therefore, weexamined oral pharmacokinetic profiles of diclofenac (DF) incattle.MATERIALS AND METHODSTotal 5 Holstein oxen, weighing 670–810 kg, were used inthis study. DF were intravenously and orally administered at adose of 1.0 mg kg1using cross over design with a 4-weekwashout period. Plasma concentration of DF were determinedby HPLC with UV-detection. Plasma concentration-time dataafter intravenous injection and oral administration were simul-taneously analyzed using a curve fitting program (MULTI) tocalculate pharmacokinetic parameters. The several parameterswere calculated by non-compartmental analysis.RESULTSThe DF kinetics after iv injection was best described by a two-compartment model. After oral administration, plasma concen-trations of DF rapidly increased and reached maximum at 2 h ofadministration and followed by similar elimination profile withiv injection.Cmaxof DF after oral administration was6.932.60lgml1. The calculated mean absorption time(MAT) was 1.610.63 h. The half-lives of absorption andelimination (bphase) were 1.510.38 h and 5.690.55 h,respectively. The oral bioavailability (F) for DF was 102%. Thevolume of distribution at steady state (Vdss) was0.0860.027 l kg1.CONCLUSIONSThis finding suggests a rapid absorption of DF from the gastro-intestinal tract. The MAT (1.61 h) of DF in this study may bedue to the fact that DF was partly absorbed from stomachbecause DF is much more lipophilic. Therefore, oral administra-tion can be used for some drugs such as DF in cattle and there-fore the problem of both tissue damage and presence of localresidues, as is often the case for drugs administered by IM andSC injection, can be avoided. |
