Comparative pharmacokinetics of gentamicin, neomycin and oxytetracycline in newborn calves

Abstract

The pharmacokinetics of three antibiotics--gentamicin, neomycin and oxytetracycline were determined in newborn calves. The kinetic determinations, using two-compartment open models, were made at increasing ages from 1 day to 42 days and compared with those made from older calves (250+ days). Although all three antibiotics are eliminated unchanged primarily by glomerular filtration, there were marked differences in the development of elimination processes for individual drugs. The pharmacokinetics of neomycin were not influenced by age. Although the elimination half-life of gentamicin appeared to decrease with age, the changes were not significant and were due to an increased elimination rate in only one calf. There was no change with age in the remaining three calves. Oxytetracycline elimination was significantly reduced in newborn calves. This was exemplified by a decrease in the half-life of elimination t1/2 (beta) from 672.5 +/- 99.4 in the newborn to 385.6 +/- 76.8 at 6 weeks of age, and 377.3 +/- 40.8 min in the 250-day-old calf. These changes were consistent in all four calves. The rate of elimination remained low for the first 4 weeks of life. The volume of distribution Vd, area was not changed after the first week of life. Based on pharmacokinetic changes, an adjustment of dosage is indicated for oxytetracycline in the newborn calf as compared to the older calf or adult.

Pharmacokinetics and Tissue Residues of Tylosin in Broiler Chickens

“…Tylosin in Tylan Soluble ® was highly distributed with great extent to all tissues V c , V d area and V dss ; (exceeded one liter/kg). This correlated with the rapid transfer of tylosin from central compartment to the peripheral one (k 12 ) than its passage from peripheral to the central compartment (k 21 ) [21] [22]; a factor revealed that tylosin is the drug of choice for attacking the systemic infections caused by sensitive organisms.…”

The influence of age on the pharmacokinetics of aditoprim in pigs after intravenous and oral administration

“…The effect of age on the disposition of some antimicrobials has been reported for a few species (Weisman et al, 1982;Brumbaugh et al, 1983;Burrows et al, 1983Burrows et al, , 1987Prescott et al, 1983;Reiche, 1983;Clarke et al, 1985). The purpose of this study was to investigate the effect of age on aditoprim pharmacokinetics in young pigs.…”

Persistence of gentamicin residues in milk after the intramammary treatment of lactating cows for mastitis

“…However, intramammary infusion of antibiotics for mastitis therapy was cited as a major reason for milk contamination (McEwen et al, 1991;Wilson et al, 1998). Gentamicin, an aminoglycoside antibiotic known to be useful in the treatment of coliform and other gram-negative pathogens (Burrows et al, 1987), is extralabely applied for the treatment of mastitis by intramammary route on some Chinese farms. Although the withholding time for gentamicin after intramammary administration has not been officially recommended, farmers and veterinarians often implement milk discard time of 5 d, as mentioned above for approved drugs.…”