JULY 28, 1997
Ask Dr. Henry: Why not use antibiotics for colds?
by Henry Hochberg, M.D.
Q: Why is antibiotic use discouraged for colds?
A: The answer to this lies in understanding the difference between viruses and bacteria. A bacteria is a complete living organism (although really, really small) while a virus is just DNA or RNA, the genetic information material, enclosed in a small, small capsule. This means the bacteria can live independently in your body, feeding, eliminating and reproducing wherever they happen to be growing. They don't depend on their host (that's you) for anything but nourishment and a place to roost for awhile. They remain outside of your bodies' cells.
Viruses, on the other hand, do not have the machinery to nourish themselves. They depend on getting inside the cell to hook up with the DNA that's already in there (that's your DNA), to be able to reproduce. They don't really need much, if any, in the way of their own nourishment since they are not independent living organisms. Once inside your own cells they use their DNA or RNA to make copies of themselves (RNA or DNA in a capsule) to spread to other cells.
Nearly all the antibiotics that you are familiar with (penicillin, amoxicillin, erythromycins, tetracyclines) are designed to interfere with the reproduction of bacteria. If the bacteria can't make offspring, the infection will disappear. The antibiotics are designed (whether by nature or by the laboratory) to attack only the bacteria. They leave your cells alone.
Viruses, because they are inside your cells, would not be affected by the familiar antibiotics. A cold is caused by a virus, and thus would not be affected by an antibiotic. If a person gets better from a cold after taking an antibiotic, my feeling is that it is either a result of the person's immune system doing the job despite the antibiotic, or that there may have been a bacterial infection in addition to the cold that the antibiotics treated.
There are specialized anti-viral drugs that work against viruses such as the herpes and AIDS viruses, but as yet there has been no effective drug designed that is successful against the hundreds of different viruses that cause the common cold.
One final note: There is a danger in taking antibiotics when they are not really needed. In this case, the bacteria living in your body (but not causing any disease) have a chance to genetically change and develop a resistance to the antibiotic. This resistance can be transmitted in various ways to other bacteria that can cause infections. Then the antibiotics become ineffective when you need them to fight the disease-causing bacteria. This is already a significant problem in our country.