pharmacological action 
Pharmacodynamics
It is a macrolide antibiotic. Gamithromycin is a semi synthetic azalactone with a 15 membered ring, mainly binding to the 50S subunit of bacterial ribosomes to prevent peptide chain elongation and inhibit bacterial protein synthesis. In vitro experimental data showed that gamithromycin exerts antibacterial effects on bovine hemolytic Escherichia coli, Pasteurella multocida, Actinobacillus pleuropneumoniae, Pasteurella multocida, and Haemophilus parasuis. The 7a position of the lactone ring of gamithromycin is alkylated nitrogen, which can be quickly absorbed under physiological pH conditions and maintained for a long time in target animal lung tissue.
Pharmacokinetics
A single dose of 6mg/kg body weight subcutaneous injection of amitocin in the neck of cattle reached the maximum blood concentration within 30-60 minutes, with a bioavailability of>98% and no gender difference. In vitro plasma protein binding studies have shown that the free drug concentration is 74%. The apparent distribution volume is 25L/kg. Jiamimycin can reach its maximum concentration in the lungs within less than 24 hours, and a lung/plasma concentration ratio greater than 264 indicates that Jiamimycin can be quickly absorbed into target tissues to combat respiratory diseases. The half-life of blood medicine is long (>2 days). Drugs are mainly excreted through bile in their original form.
A single dose of intramuscular injection of amitocin at a dose of 6mg/kg body weight in the neck of pigs reached the maximum blood concentration within 5-10 minutes, with a bioavailability of>92%. The in vitro plasma protein binding test showed a free drug concentration of 77%. The apparent distribution volume is 39L/kg. Jiamimycin can be quickly absorbed into target tissues to combat respiratory diseases. The concentration of gamithromycin in the lungs is much higher than that in the blood, and the blood drug has a long half-life (about 4 days). The drug is mainly excreted through bile in its prototype form.
Indications
Used to treat bovine respiratory diseases caused by hemolytic Escherichia coli, Pasteurella multocida, and Mycoplasma, which are sensitive to gamithromycin; Respiratory diseases in pigs caused by Actinobacillus pleuropneumoniae, Pasteurella multocida, and Haemophilus parasuis.