PHARMACOKINETICS OF ENROFLOXACIN IN NEWBORN AND ONE-WEEK-OLD CALVES

The pharmacokinetic behaviour of enrofloxacin was compared in four one -day-old and four one-week-old calves in order to find out if there we re any age-related differences. Mean volume of distribution (V-d(ss)) and clearance (Cl) were significantly smaller in newborn calves: V-d(s s) was 1.8 and 2.3 L/kg, while clearance was 0.19 and 0.39L/kg.h in ne wborn and one-week-old calves, respectively, Mean elimination half-lif e (t(1/2 beta)) did not differ significantly in newborn and in one-wee k-old calves: mean t(1/2 beta) was 6.6h and 4.9h, respectively, Enrofl oxacin was metabolized to ciprofloxacin both by newborn and one-week-o ld calves, but the maximum concentration (C-max) of ciprofloxacin was lower and the time when maximum concentration was reached (t(max)) lat er in newborn calves. We conclude that the dosage of enrofloxacin shou ld be adjusted according to age when administered to very young calves .