SERUM AND MILK CONCENTRATIONS OF APRAMYCIN IN LACTATING COWS, EWES AND GOATS

A 20% solution of apramycin was administered intravenously (i.v.) and intramuscularly (i,m,) to lactating cows with clinically normal and ac utely inflamed udders, to lactating ewes with normal or subclinically infected, inflamed udders and i,v. to lactating goats with normal udde rs, The i,v, disposition kinetics of apramycin was very similar in cow s, ewes and goats. The elimination half-life was approximately 2 h and the steady-state volume of distribution was 1.26-1.45 L/kg, The absor ption rate of the drug from the i,m, injection site was rapid, the i,m . bioavailability was 60-70% and the mean elimination half-life was 26 5 min in cows and 145.5 min in ewes. The binding percentage of apramyc in to serum protein was low (< 22.5%), Concentrations of apramycin in milk produced by clinically normal mammary glands of cows, ewes and go ats were consistently lower than in serum; the kinetic value AUC(milk) /AUC(serum) was < 0.32, Drug penetration into the milk from the acutel y inflamed quarters of cows was extensive; mastitis milk C-max values were more than tenfold greater than the C-max in normal milk, On the o ther hand, the drug had limited access to the milk produced by subclin ically infected inflamed half-udders of ewes.