Vetrinary Drug Information 2020-10-22
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1. Synergistic effect of combined application of veterinary drugs
The combined application of penicillin + streptomycin has clinical significance. Synergy and additive effects can often be obtained. Such as: colistin + tiamulin, spectinomycin + lincomycin, neomycin + oxytetracycline; kanamycin + TMP and so on. Since they are all antibacterial drugs, synergistic effects are generally obtained. Such as: Tylosin + Sulfa + TMP, Tiamulin + Sulfa + TMP, Lincomycin + Sulfa + TMP, Oxytetracycline + Sulfa + TMP and so on. Because fluoroquinolone drugs have a synergistic effect at the same time as a combination application. Such as: Enrofloxacin + Amoxicillin, Enrofloxacin + Colistin, Enrofloxacin + Lincomycin, Enrofloxacin + TMP, etc.


2. Antagonistic effect of combined application of veterinary drugs
Penicillin cannot be combined with florfenicol, tetracyclines, macrolides, and lincomycin.


Because these four can quickly inhibit the synthesis of bacterial protein and keep the bacteria in a static state where the growth and reproduction of the bacteria are stopped, the penicillin of the fungicide during the breeding period can not be fully exerted when it interferes with the synthesis of the cell wall, which reduces the efficacy of penicillin. Amoxicillin should not be added to the feed at the same time as the third class of drugs. Although pharmacologically, the combination of amoxicillin and chlortetracycline or florfenicol may be improper, but clinical use does not seem to cause adverse reactions.


Although fluoroquinolone drugs have both the first and second properties at the same time, it also highlights its shortcomings, that is, it has a partial antagonistic or weakening effect with the third and fourth types.
 
3. There is no synergy and weakening in the combined application of veterinary drugs
Combination of fungicides and slow-acting bacteriostatic agents during the breeding period, although generally no enhancement or weakening effect, will not have a major effect or antagonistic effect. Because of its poor killing effect on bacteria whose metabolism is inhibited, it is generally not suitable for joint application. So when injecting penicillin, there is no need to inject sulfa drugs at the same time. An exception is the treatment of encephalitis. When there are obvious indications, sulfadiazine sodium and penicillin can be injected intramuscularly separately (not mixed), which can improve the efficacy of the drug in the treatment of brain bacterial infections.


Fourth, the combined application of veterinary drugs increases the toxicity or decreases the efficacy of the same combination
Combination of similar drugs is not suitable. For example, streptomycin, gentamicin, kanamycin, etc. among aminoglycosides should not be used in combination, otherwise it will increase ear and nephrotoxicity. The same class of antibacterial drugs, such as florfenicol, macrolides, lincomycins, and tylosin have the same mechanism of action. They all act on the 50S subunit of the bacterial ribosome to inhibit the elongation of the peptide chain. It hinders bacterial protein synthesis and produces rapid antibacterial effect. They cannot be combined with each other, otherwise antagonism may occur. If florfenicol cannot be combined with the latter three (macrolides, lincomycins, tylosin), the latter can replace or prevent florfenicol and 50S subunits due to the competition site The combination produces an antagonistic effect, resulting in weakened efficacy.


Five, the combined application of veterinary drugs synergistically increases the efficacy
Florfenicol and doxycycline, tiamulin + chlortetracycline, tylosin + oxytetracycline;


Bacitracin zinc + colistin, sulfa + TMP, etc.


Sixth, the combination of combination drugs


1. Tyvanicin and Florfenicol
Tyvanectin is the latest generation of animal-specific macrolide drugs. Compared with other macrolide drugs, its efficacy has been significantly improved. It has a unique effect on mycoplasmosis, PRRS virus infection and proliferative ileitis. Florfenicol has a good effect on infectious diseases of the respiratory and digestive tracts of livestock and poultry. The above-mentioned combined dosing regimen has been widely recognized by farmers in preventing respiratory diseases in nursery pigs and fattening pigs, improving the resistance of pregnant sows, and preventing thoracic transmission and mycoplasmosis. To prevent the lack of nutrient elements). In addition, Tilmicosin or Tiamulin also showed certain efficacy.


2. Albendazole + Ivermectin
Albendazole is a benzimidazole derivative and a broad-spectrum insect repellent; Ivermectin is a derivative of the macrolide antibiotic abamectin, which has outstanding insecticidal activity and a broad insecticidal spectrum. Especially it has a strong killing effect on arthropod insects and nematodes in the body such as gastrointestinal nematodes and lung nematodes, but ivermectin has a poor killing effect on tapeworms and trematodes, so the combination of albendazole + ivermectin is used Administration (golden ratio 50:1) can strengthen the repellent effect on various parasites in and out of the body.


3. Quinenone + flavomycin
Quinenone is a quinoxaline dioxide derivative, which has antibacterial, antidiarrheal and growth-promoting effects; flavomycin is a phosphorylated polysaccharide antibiotic. Compared with its antibacterial characteristics, it improves feed utilization and promotes livestock and poultry. The role of growth is more concerned. Studies have shown that adding quinenone + flavomycin (5:1) in a certain proportion of pig feed (flavomycin can be added less in poultry feed), the pig’s daily gain (ADG) and protein digestibility are improved, and it can be effective at the same time. Reduce the rate of diarrhea. Considering the cost of use and the effect of growth promotion, the feed supplement of quinenone + flavomycin is highly regarded by farmers.


4. Lincomycin + Spectinomycin
Spectinomycin is an aminoglycoside antibiotic and has a good effect on gram-negative bacteria. Lincomycin is a lincosamide antibiotic and has a strong antibacterial effect on gram-positive bacteria. The combination of the above two antibiotics does not interfere with each other's pharmacodynamic characteristics, can expand the antibacterial spectrum, and has a good effect on piglet diarrhea, mycoplasma pneumonia and chicken respiratory diseases.


5. Combination of sulfa synergist and various drugs
Antibacterial synergists (sulfa synergists) such as trimethoprim (TMP), whose principle is to inhibit dihydrofolate reductase so that dihydrofolate cannot be reduced to tetrahydrofolate, thus blocking the metabolism of sensitive bacteria. The combination of TMP and sulfonamides in a ratio of 1:5 can inhibit the synthesis of bacterial folic acid in two stages, thereby turning the bacteriostatic effect of sulfa drugs administered alone into a bactericidal effect. Not only sulfa formulations can achieve better efficacy, but studies have shown that the antibacterial effect of tetracycline, gentamicin and TMP can also be enhanced when combined.


6. Common combination drugs
Amoxicillin+clavulanate potassium and prednisolone are used in the treatment of cow mastitis; tiamulin and chlortetracycline are used in the treatment of Mycoplasma gallisepticum.