Disposition of gentamicin in the genital tract of cows*

Abstract
The distribution of gentamicin (G) in plasma and uterine lumen was studied following intramuscular (i.m.) and intrauterine (i.u.) treatment. A Foley catheter was inserted into one uterine horn and retained in place by inflation of the cuff. This provided a closed system for collection of uterine lumen samples and analysis of the concentration of gentamicin for 6 h following treatment. Four normal cycling and healthy cows in dioestrus were given i.m. injections of 4 mg gentamicin/kg BW and another two were given i.m. injections of 2 mg gentamicin/kg BW gentamicin. The uteri were infused with 50 ml saline containing phenolsulphonphthalein (PSP) indicator. Blood and infused solution (IS) samples were periodically collected during the 6‐h period following i.m. administration. Six hours after injection, approximately 183.7 μg gentamicin and 39.4 μg gentamicin were accumulated in the uterine lumen of cows receiving 4 mg gentamicin/kg BW and 2 mg gentamicin/kg BW, respectively. The amount of gentamicin reaching the blood stream after i.m. administration of 4 mg gentamicin/kg BW was 2.89 times that reached after administration of 2 mg gentamicin/kg BW based on the area under the curve of plots of plasma concentration of gentamicin versus time. Four normal‐cycling and healthy cows in dioestrus were given i.u. infusions of gentamicin (225–275 mg) diluted in 50 ml saline containing PSP indicator using a Foley catheter in a closed system. Samples from the IS and blood were collected at various intervals for 6 h after infusion. Following i.u. infusion of gentamicin, an average of 29.4% of the dose was absorbed into the bloodstream. The majority of the dose of gentamicin (70.6%) remained in the uterine lumen throughout the 6‐h period.

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