What Are Antibiotics?
These powerful drugs treat many bacterial infections, but experts fear they may be overprescribed.
Antibiotics are a group of prescription drugs used to treat a wide variety of infections caused by bacteria.
They aren’t effective against fungal or viral infections, such as a cold or flu, notes MedlinePlus. There are other drug classes designed to treat those infections.
There are many different classes and subclasses of antibiotics, some of which include:
- Penicillins, such as amoxicillin (Amoxil), amoxicillin-clavulanic acid (Augmentin), and ampicillin-sulbactam (Unasyn)
- Cephalosporins, including cefdinir (Omnicef), ceftriaxone (Rocephin), and cephalexin (Keflex)
- Fluoroquinolones (quinolones), like levofloxacin (Levaquin), ciprofloxacin (Cipro), and moxifloxacin (Avelox)
- Macrolides, such as azithromycin (Zithromax) and erythromycin (MY-E)
- Tetracyclines, including tetracycline (Sumycin) and doxycycline (Vibramycin)
- Lincosamides, like clindamycin (Cleocin) and lincomycin (Lincocin)
- Aminoglycosides, like amikacin (Amikin), gentamicin (Gentak), tobramycin (Tobi), and neomycin
- Sulfonamides (sulfa drugs), such as Septra and sulfamethoxazole and trimethoprim (Bactrim)
Not all antibiotics work the same way to fight infections.
Some antibiotics are bactericidal, meaning that they kill bacteria, while others are bacteriostatic, meaning that they prevent bacteria from reproducing, as noted by Compound Interest.
For example, penicillins, cephalosporins, and aminoglycosides are bactericidal, while macrolides, tetracyclines, and sulfonamides are bacteriostatic.
Warnings and Precautions
Since allergies to certain antibiotics like penicillins and sulfa drugs are common, it’s always a good idea to find out what class or subclass your prescribed antibiotic is in.
Unless your doctor tells you otherwise, be sure to finish taking all of the antibiotics you were prescribed — even if you start to feel better.
This is extremely important to make sure the infection goes away completely. If you fail to finish the entire course of therapy, the infection may still be present, and symptoms may return.
Then, if the infection comes back, it may be more difficult to treat.
It’s also possible that the antibiotics your doctor originally prescribed may not work as well — or at all — because the bacteria may have become resistant to the original drug.
Antibiotic Resistance
Bacterial resistance to antibiotics is a widespread problem, as the Centers for Disease Control and Prevention (CDC) has noted.
In fact, some antibiotics that were effective against certain infections just a few years ago are no longer useful.
Misuse and overuse of antibiotics contribute to bacterial resistance. Resistance occurs when bacteria develop the ability to continue growing, despite the presence of a particular antibiotic.
The CDC estimates that at least 30 percent of antibiotic prescriptions are not needed — in most cases, the patient’s issues are due to viral, and not bacterial, infections; and overall misuse of antibiotics, such as improper prescriptions or not following the full course of treatment, is as high as 50 percent.
Further, as the University of Minnesota notes, most of the antibiotics used in the United States (as many as 70 percent) are not provided to sick people, but are given to farm animals to prevent disease and encourage growth.
Resistance may occur when antibiotics are taken for a condition that isn’t caused by bacteria, such as:
- Cold
- Flu (influenza)
- Viral gastroenteritis (“stomach flu”)
- Most coughs
- Most sore throats
There’s no benefit from taking antibiotics for viral or fungal infections, and doing so may put you and others at risk for antibiotic-resistant infections down the line.
General Side Effects
Although most people can take antibiotics successfully, possible side effects include:
- Sun sensitivity
- Stomach upset
- Diarrhea
- Vaginal yeast infection
- Metallic taste in the mouth
- Allergy to the drug, resulting in rash or hives
- Severe, potentially life-threatening swelling due to drug sensitivity, called anaphylaxis
However, in more severe cases, some antibiotics may cause a very severe form of diarrhea that is characterized by frequent episodes of loose, watery stools with a strong odor that is much more unpleasant than normal.
If this happens, stop taking the antibiotic immediately and contact your doctor right away. You may have to take a different antibiotic.
Certain antibiotics may cause such side effects as tooth discoloration in baby teeth, hearing loss, or kidney problems.
Drug Interactions
But other antibiotics, like fluoroquinolones and tetracyclines, don’t work as well if you take them at the same time as calcium, iron, antacids like Tums or Maalox, or foods such as milk, cheese, or nuts.
Be sure to tell your doctor if you’re taking medications or supplements that contain calcium or iron or eating dairy foods or nuts.
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Resources
- Antibiotics. MedlinePlus. January 14, 2022.
- A Brief Overview of Classes of Antibiotics. Compound Interest. September 8, 2014.
- About Antimicrobial Resistance. Centers for Disease Control and Prevention. October 5, 2022.
- Antibiotics: Are You Misusing Them? Mayo Clinic. July 11, 2023.
- Measuring Outpatient Antibiotic Prescribing. Centers for Disease Control and Prevention. October 5, 2022.
- FDA: Antibiotic Use in Food Animals Continues to Rise. University of Minnesota. December 22, 2016.