Neomycin sulfate for veterinary use, along with kanamycin and gentamicin, all belong to the aminoglycoside class of antimicrobials, and the most widely used in veterinary treatment clinics is neomycin sulfate soluble powder. Neomycin sulfate is easily soluble in water, and the aqueous solution is acidic; its stability in drinking water is very good, and the nephrotoxicity of injectable use is strong, which is the reason why neomycin sulfate is given orally in large quantities in veterinary clinics for livestock and poultry.
Normally, the intact gastrointestinal tract absorbs very little neomycin sulfate from oral intake (generally no more than 3%). However, if the gastrointestinal tract is ulcerated, the mucosa is detached or there is inflammation, the gastrointestinal tract absorbs neomycin sulfate in larger quantities. Neomycin sulfate entering the body can be distributed to the heart, liver, spleen, lung, kidney and other organs and some tissues, but the dose of the drug absorbed into the body by oral intake is far from the effective therapeutic dose.
The antibacterial effect of neomycin sulfate is to enter the cells of bacteria before it can bind to the 30S subunit of ribosome, thus inhibiting the synthesis of bacterial protein and achieving the bactericidal effect. The antibacterial effect of amoxicillin is achieved by irreversibly destroying the bacterial cell wall, which has a rapid bactericidal effect. Thus, neomycin sulfate and amoxicillin are formulated as a veterinary prescription, and amoxicillin opens the portal for neomycin sulfate to enter the bacterial cells freely, and this synergistic effect can significantly enhance the antibacterial efficacy of neomycin sulfate and amoxicillin.
Neomycin sulfate absorbed into the organism can be rapidly distributed to all tissues and organs of the body. The highest concentration is distributed in heart, liver and kidney, mainly concentrated in nucleated cells (higher content in white blood cells). Within 24h, about 12%-25% of neomycin sulfate is excreted by the kidney; about 50%-90% is excreted by the bile, so its effect on the intestine is better. The plasma elimination half-life of neomycin sulfate is long, about 36h, due to the slow release of neomycin sulfate absorbed into the body from storage tissues.
Amoxicillin is better absorbed orally. Such a large amount of amoxicillin entering the body can play a synergistic antibacterial role with the larger amount of neomycin sulfate that has already entered the organism, and this synergistic antibacterial effective therapeutic dose of neomycin sulfate only requires a 5:1 amount of amoxicillin over neomycin sulfate is sufficient. In this way, the effective amoxicillin absorbed orally into the body is ensured to be not less than 20mg/kg body weight, and only 4mg/kg body weight of neomycin sulfate is needed to make the prescription of “neomycin sulfate + amoxicillin” very effective.
