Comprehensive Collection of Common Sense on Veterinary Drugs

Common sense about medications:

What is a drug:

Medicines are substances used to prevent and treat diseases in livestock (such as cattle, sheep, and pigs) and poultry (such as chickens, ducks, geese, and pigeons).
Classification of Commonly Used Veterinary Drugs:

Antibacterial drugs, antiviral drugs, antiparasitic drugs, and the like.

Classification: Antibacterial agents are further divided into two categories: antibiotics and synthetic antibacterials. So-called antibiotics are metabolic products produced by microorganisms; these metabolic products have the effect of inhibiting the growth or killing certain other microorganisms. Synthetic antibacterials, on the other hand, are antibacterial substances synthesized chemically by humans—rather than being produced through microbial metabolism. Antibacterial agents are classified into two main categories: antibiotics and synthetic antibacterials.

I. Antibiotics: Antibiotics are typically classified into eight categories:

1. Penicillin class: penicillin, ampicillin, amoxicillin, etc.;

2. Cephalosporins (cephamycins): cefalexin, cefadroxil, cefuroxime, cephalosporin, and others;

3. Aminoglycosides (pronounced similarly to “dai”): Streptomycin, Gentamicin, Amikacin, Neomycin, Apramycin, and others;

4. Macrolides: erythromycin, clarithromycin, tylosin, etc.;

5. Tetracyclines: oxytetracycline, doxycycline, chlortetracycline, tetracycline, etc.;

6. Chloramphenicol class: florfenicol, thiamphenicol, etc.;

7. Lincosamide antibiotics: lincomycin, clindamycin, etc.;

8. Other categories: Colistin sulfate, etc.
(1) Penicillins:

Source: Penicillins are a class of β-lactam antibiotics whose core structure is the penam ring. They are either extracted from the fermentation broth of Penicillium fungi or further prepared through semisynthesis (both penam and lactam refer to specific chemical structures).

Mechanism of action: Penicillin-class drugs interfere with the synthesis of bacterial cell walls, causing defects in the newly formed cell walls and leading to bacterial lysis. At lower concentrations, they only inhibit bacterial growth; at higher concentrations, they exhibit potent bactericidal activity. They exert strong antibacterial effects against most Gram-positive bacteria, certain Gram-negative bacteria, various spirochetes, and actinomycetes. [Gram staining is a bacterial staining technique that classifies bacteria into Gram-positive and Gram-negative based on their different staining characteristics after being stained.]

Currently, antibiotics are generally classified into four major categories:

The first category is bactericidal agents for the reproductive phase: these agents are most effective against bacteria during their rapid, massive proliferation stage and primarily exert a bactericidal effect. Common examples include penicillins and cephalosporins.

The second category is bactericidal agents that act during the stationary phase: these agents are most effective against bacteria during the phase when bacterial reproduction is relatively inactive, and their primary function is to kill bacteria. They typically include aminoglycosides and polymyxins from other classes.

The third category is rapid bacteriostatic agents: These drugs can swiftly inhibit bacterial growth and reproduction, slowing down the rate at which bacteria multiply and greatly extending the growth and reproduction cycle of individual bacteria. However, they do not directly kill bacteria. This category typically includes chloramphenicol, macrolides, tetracyclines, and lincomycins, among others. The fourth category is slow-acting bacteriostatic agents: These drugs can slowly inhibit bacterial growth and reproduction. They typically include sulfonamides and the synergist TMP (trimethoprim).

Generally speaking, combinations of Class 1 and Class 2 can produce synergistic effects (i.e., enhanced efficacy). Combinations of Class 3 and Class 4 can result in additive effects (i.e., enhanced overall effect). Combinations of Class 1 and Class 3 may exhibit antagonistic effects (i.e., reduced efficacy). Combinations of Class 1 and Class 4 may also exhibit antagonistic effects (i.e., reduced efficacy). When antibiotics of the same class are used in combination, some combinations may enhance efficacy, while others may reduce it.

1. Penicillin-class and sulfonamide drugs, as well as sulfonamide potentiators, are incompatible with each other; for example, ampicillin and Bactrim (sulfamethoxazole) must not be mixed.
       
2. Penicillins and tetracyclines are incompatible; for example, ampicillin and doxycycline should not be mixed.

3. Penicillins and macrolides are incompatible; for example, ampicillin and erythromycin should not be mixed.

4. Penicillins and chloramphenicols cannot be mixed; for example, amoxicillin and flufenicol should not be combined.

5. Penicillins and aminoglycosides can be combined; for example, penicillin and streptomycin can be combined, as can ampicillin and apramycin. However: penicillins and gentamicin cannot be combined, because penicillins reduce the activity of gentamicin.

6. Penicillins and colistin sulfate can be used in combination.

7. Ampicillin and vitamin C cannot be mixed.