Home Medical Care: antibiotics


Technically, antibiotics are chemical substances produced by microscopic organisms that interfere with the growth of other microorganisms. In practice, antibiotics include a large number of substances, many synthetically made, that are used primarily in the treatment of bacterial infections. Antibiotics are miracle drugs when properly used. They enable us to cure infections that in the past would have certainly been fatal. They can, however, be easily misused.

All antibiotics are not effective against all bacteria. A veterinarian’s decision to use a particular antibiotic is based on the probable bacterium causing the disease and/or the results of laboratory tests in which the infective organisms are grown and tested for antibiotic sensitivity. If the wrong antibiotic is chosen, there is no beneficial effect. If the proper antibiotic is chosen and given at the correct dosage, growth of the bacteria is stopped or at least controlled sufficiently that the body’s own natural defense systems can overcome the infection.

If the antibiotic is not given as frequently as prescribed or if the medication is discontinued too soon, forms of bacteria resistant to the antibiotic may multiply, or the infection may recur. Antibiotics are not always effective alone. Other drugs and special nursing techniques must often be combined with their use. In cases of localized infection such as abscesses, antibiotic treatment must often be used with proper surgical intervention for success.

Many people seem to believe that antibiotics are useful in combating any infectious or febrile disease. This is certainly untrue. A particularly common case where antibiotics may be of no help is the viral infection.


Viruses exist in body cells and depend on the cells metabolic process for reproduction. Since the methods of viral metabolism are unlike those of bacteria, which for the most part survive outside of cells and multiply independently, drugs effective against bacteria are ineffective against viruses. When antibiotics are prescribed for use during viral infection, it is to combat bacteria that invade after the virus has weakened the animal (secondary infection). There are very few drugs available for treatment of viral infections. Since viral reproduction is so intimately tied to normal cellular function, most drugs found effective against viruses also destroy body cells.


Like other drugs, most antibiotics have potential side effects. Since bacteria are single-celled organisms similar in many ways to individual body cells, antibiotics can sometimes act against body cells in ways similar to the ways they adversely affect bacteria. Among the possible side effects are allergic reactions, toxic effects, alteration of metabolism, and alteration of normal (and beneficial) bacteria inhabiting the body. A good veterinarian will tell you if there are any side effects you should watch for when antibiotics are prescribed. Side effects can be made more likely by the use of outdated drugs, combining antibiotics with certain other drugs, and by certain illnesses.

Indiscriminate use of antibiotics is to be avoided. Use with proper guidance will avoid toxic effects and stem the development of antibiotic-resistant bacteria. Be glad, not disappointed, if your veterinarian feels that the condition can be treated without antibiotics (or other drugs) and sends you away empty-handed. And don’t use leftover antibiotics unless directed to by your veterinarian. Antibiotics are available over the counter as ointments for topical (on the body surface) use.

Common effective ones contain bacitracin, neomycin, and/or polymixin B. These are suitable for applying to superficial wounds to achieve a local antibacterial effect. They should not be applied into deep wounds, as the carrier ointment for the drugs may interfere with healing.