Antibiotics are used to fight against bacterial infections and parasites, and thus there are many different kinds of prescription antibiotics doctors may use to treat illness. With such a wide range of options, it can be difficult knowing why exactly you were prescribed a certain antibiotic, or what its side effects are.


These are the most common antibiotics:


Penicillin was not only the first antibiotic but one of the most widely used antibiotics today. Over time, other types of the drug were developed, including amoxicillin, ampicillin, and penicillin types V and G. All penicillins are derived from penicillin notatum, a type of mold that eats and prevents bacteria from growing. The active agent of this mold, penicillin, is extracted from it to create the antibiotic. Its side effects include the rare allergic reaction, which can vary from hives to anaphylaxis depending on the individual. Thus, doctors test penicillin reactions in tiny doses when we are children.


Penicillins work by weakening the cell walls of bacteria infecting the body, making it easier for antibodies to fight off infection. It is mostly used to treat illnesses like pneumonia, upper respiratory infections, strep throat, and meningitis.


Clindamycin works best for lung, skin, and blood infections. It may also be used to treat infections in female reproductive organs as well. The drug itself works by stopping the growth and spread of bacteria, leaving it unable to reproduce and thus more manageable for the body’s immune system.


Clindamycin is a heavy-duty antibiotic, meaning it is used primarily for serious infections. Someone may be prescribed clindamycin for infections that haven’t gone away after several weeks, or if an infection is accompanied by a fever. Side effects include nausea, joint pain, difficulty swallowing, an unpleasant taste in the mouth, and heartburn. Similar to penicillin, people can be allergic to clindamycin.


Tetracyclines are most often used to treat respiratory infections but are also used for skin, eye, intestinal, lymphatic, genital, and urinary infections as well. Infections spread by ticks, mites, lice, and infected animals are also treatable via tetracyclines.


Since it is a common alternative to penicillins, tetracyclines work similarly to penicillins. By inhibiting specific enzyme processes, tetracyclines prevent bacteria from reproducing and sending important signals to other bacteria, which in turn makes it easier for the body to fight them off. Side effects include nausea, vomiting, diarrhea, sore throat, and a swollen tongue.


Cephalosporins block the production of enzymes used to make a bacteria’s cell wall, just like penicillins do. However, cephalosporins are used most often to treat ear infections, urinary tract infections, and skin (or soft tissue) infections alongside meningitis, strep throat, and pneumonia. Cephalosporins are another common penicillin alternative, and scientists are often developing stronger, more effective forms of the drug to combat bacterial evolution. In serious infections, cephalosporins are sometimes administered through an IV.


Cephalosporins may cause diarrhea, nausea, vomiting, dizziness, and yeast infections. It is also possible for someone to be allergic to cephalosporins.


Sulfonamides, better known as sulfa drugs, are a type of antibiotic that is mainly derived from sulfanilamide. Sulfonamides work by disrupting the production of folic acids in bacteria, leaving them unable to produce proteins.


Since they are a general antibiotic, we see sulfonamides quite frequently prescribed for a number of infections, but some sulfonamides are developed specifically to treat ulcerative colitis. Side effects of sulfonamides include nausea, diarrhea, vomiting, loss of appetite, headaches, dizziness, and lethargy.


If you have any questions about a prescription, ask your primary care physician or a pharmacist for more information.

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