There are many therapeutic drugs for livestock and poultry respiratory diseases, but it is difficult for the vast number of clinical first-line veterinarians to use them well and achieve results in every clinical livestock and poultry clinic! The reason is that everyone's existing pharmacological knowledge is basically learned from universities and books, and it is not practical!
  Because the pharmacological knowledge in the books is basically the indicators and parameters made by mice, rabbits or livestock and poultry health animal laboratories; and the drugs we see in clinical practice are all sub-healthy and pathological cases. Those things in the books need to be explored, experienced and summarized into practice in production practice, that is, applied pharmacology.
  Therefore, when it comes to this, applied pharmacology is the pharmacology of drugs after the combination of theory and production practice. It comes from books, from the principles and mechanisms in books; but it is quite different from books, specific diseases require specific drugs, specific mechanisms require technical compatibility (prescription), specific prescriptions require special usage, and so on.
  For example, doxycycline and tilmicosin. These two drugs are alkaline antibiotics, and the pH value of the extracellular fluid is about 7.3-7.6 under normal circumstances. It is easier to transport from the outside to the inside of the cell, that is, tilmicosin and doxycycline are easy to accumulate in the cell, that is, the concentration of these two drugs distributed inside the cell is much higher than that outside the cell.
  The pH value of the intracellular fluid of livestock and poultry is about 7, and in most cases it is a weakly acidic environment; as for pathogens that parasitize, replicate, and reproduce in cells such as PRRS virus, influenza virus, and Newcastle disease, they need The acidic intracellular fluid environment.
  It is conceivable that when a large amount of tilmicosin and doxycycline enter the cell, the pH value of the intracellular fluid changes from acidic to alkaline, which will cause viruses that need to replicate, assemble and multiply in the cell, so The pH value of the intracellular fluid on which it relies suddenly becomes alkaline and does not adapt, causing the replication of the virus in the body to be inhibited.
  Looking at the infection of respiratory diseases in livestock and poultry in autumn and winter, most of them have the participation of viruses (some are dominant, some are recessive). In this case, for the treatment of respiratory diseases of livestock and poultry in autumn, using antiviral drugs in combination with these two drugs is better than using other drugs that have the same efficacy or are more effective than them (such as tyvanectin). Drugs are the reason why they have excellent clinical application effects.
  Of course, these just let us understand the reason (principle) that the combined prescription of tilmicosin and doxycycline for the treatment of livestock and poultry respiratory diseases is better than other drugs. To truly maximize the application and prescription technologies of these two drugs, more pharmacological applications of these two drugs are needed. For example, what are the differences in their pharmacology in target animals such as pigs, chickens, and ducks, so as to improve the skills of using these two drugs on different animals. This also requires everyone to experience, summarize and improve in production practice.

https://www.arshinepharma.com/info/tilmicosin-and-doxycycline-the-use-of-these-t-78337273.html