Distribution of neomycin in bull calves after intramuscular injection.

Neomycin sulfate was injected intramuscularly in calves. Blood and tissue samples were taken at zero, one, two, four, six, eight and 24 hours after administration. The tissues with high levels (greater than 10 mug/g) of drug at the one hour period were kidney cortex and medulla, urine, blood serum and the injection site. By 24 hours after administration only the kidney cortex and urine had high levels of neomycin. The drug could not be detected in any brain tissues and very small amounts (less than 1 mug/g) were present in the bile, thymus and vitreous humor. Levels greater than 5 mug/g were present in lung tissues for less than four hours but were greater than 2 mug/g for more than 24 hours.The mean level in the injection site was greater than 700 mug/g at one hour but only trace amounts were found at 24 hours.On the basis of the tissue drug concentration intramuscularly administered neomycin was suggested as therapeutically useful for respiratory and urinary tract infections caused by susceptible bacteria.