Antibiotics 101: What You Should Know About These Medicines

Antibiotics 101: What You Should Know About These Medicines
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Medically Reviewed By:
Mark Arredondo, M.D.

Antibiotics are lifesaving drugs that help combat bacterial infections, but they can be misused.

This article will dive into the topic of antibiotics, understanding what they are, how they function, the types available, what infections they treat (and what they can't help with), their potential side effects and the important topic of antibiotic resistance.

What are antibiotics?

Antibiotics work by either stopping bacteria from growing or eliminating them. As per the Cleveland Clinic, these medications come in different forms:

  • Oral antibiotics: Taken by mouth, they can be tablets, capsules or liquids

  • Topical antibiotics: Applied on the outside of the body, like creams, ointments or drops to treat specific infections

  • Injections and IV antibiotics: Administered by a health care provider through a shot into your muscle or an IV in your vein. These forms are used for more severe infections

Taking antibiotics for the full prescribed course is vital to ensure successful treatment. Common antibiotics include:

  • Gentamicin (also amikacin, neomycin, streptomycin, tobramycin)

  • Ertapenem (also imipenem, meropenem)

  • Cephalexin (also cefuroxime, ceftriaxone, ceftazidime)

  • Ciprofloxacin (also levofloxacin, moxifloxacin)

  • Clindamycin

  • Erythromycin (also clarithromycin, azithromycin)

  • Metronidazole

  • Benzylpenicillin (also amoxicillin, piperacillin, ticarcillin)

  • Sulfamethoxazole and trimethoprim ("Septrin")

  • Tetracycline (also doxycycline, minocycline)

How do antibiotics work?

Antibiotics are essential in treating bacterial infections but come in different types. Some are highly specialized and effective against specific bacteria, while those known as broad-spectrum antibiotics combat a wide range of bacteria.

The Microbiology Society indicates that these medications work primarily in two ways: they either inhibit bacterial reproduction or, in some cases, they kill the bacteria. This can be achieved by interfering with vital processes, like halting the construction of bacterial cell walls.

What are antibiotics used for?

Antibiotics are vital in treating or preventing certain bacterial infections by killing bacteria or preventing their multiplication and spread.

Antibiotics are sometimes given as a precaution, known as antibiotic prophylaxis, for wounds with a high risk of infection, such as animal or human bites, soil or feces exposure. Certain medical conditions, like a compromised spleen, chemotherapy or sickle cell anemia, make people more susceptible to infections and thus require antibiotic prophylaxis.

Recurring infections like cellulitis, urinary tract infections, genital herpes, or rheumatic fever may also warrant antibiotic prophylaxis.

What can antibiotics not help with?

It's important to note that antibiotics don't work against viral infections and they are not routinely prescribed for mild bacterial infections, as the immune system can often handle those on its own.

More specifically, the U.S. Centers for Disease Control and Prevention (CDC) indicates that antibiotics are ineffective against viral infections, including those responsible for:

  • Common colds and runny noses, regardless of mucus color

  • The majority of sore throats (excluding strep throat)

  • Influenza (flu)

  • Most instances of chest colds, like bronchitis

Types of antibiotics

Antibiotics come in various types, often grouped into six categories:

  • Penicillins: These are commonly employed to treat diverse infections, such as skin, chest, and urinary tract infections

  • Cephalosporins: Effective against many infections, some are suitable for severe conditions like septicemia and meningitis

  • Aminoglycosides: Primarily used in hospitals for serious illnesses like septicemia, but can have side effects like hearing loss and kidney damage. Administered by injection, they may also be given as ear or eye drops for specific infections

  • Tetracyclines: Useful for a wide array of infections and frequently prescribed for moderate to severe acne and rosacea

  • Macrolides: Particularly effective for lung and chest infections and are alternatives for those with penicillin allergies or penicillin-resistant bacterial strains

  • Fluoroquinolones: Broad-spectrum antibiotics for a wide range of infections

Side effects of antibiotics

The CDC says that using antibiotics when they aren't necessary provides no benefit and can cause harm. Common side effects of antibiotics may include:

  • Rash

  • Dizziness

  • Nausea

  • Diarrhea

  • Yeast infections

More serious side effects:

  • Clostridioides difficile infection (C. difficile or C. diff), causing severe colon damage and potential death

  • Severe, life-threatening allergic reactions

Can you drink on antibiotics?

Combining antibiotics and alcohol can lead to similar side effects, such as stomach discomfort, dizziness and drowsiness, which may be intensified.

The Mayo Clinic explains that certain antibiotics like metronidazole (Flagyl), tinidazole (Tindamax), sulfamethoxazole and trimethoprim (Bactrim) should never be combined with alcohol due to the risk of severe reactions. Consuming any amount of alcohol alongside these medications can contribute to side effects like nausea, vomiting, flushing, headache and rapid heart rate.

Additionally, linezolid (Zyvox) interacts with specific alcoholic beverages, including red wine and tap beer, leading to potentially dangerous increases in blood pressure.

Remember that some cold medicines and mouthwashes contain alcohol, so always check labels and avoid such products when taking these antibiotics.

While moderate alcohol consumption typically doesn't affect the efficacy of most antibiotics, it can lower your energy and slow your recovery from illness. Health care providers typically advise patients to abstain from alcohol until they've completed their antibiotic treatment and feel better.

Antibiotic resistance

Dr. Karen Coffey, medical director of infection control for the VA Maryland Health Care System, said in a recent interview that, “Antibiotics are one of the main resources that we have and as we lose those resources, we don’t make up the ground in other ways. So it absolutely is a threat and is something that every hospital is addressing.”

Antibiotic resistance develops when bacteria develop the ability to survive drugs meant to eliminate them, according to the CDC. This means the germs not only survive, but also continue to multiply. Resistant infections can be challenging and sometimes impossible to treat.

This issue poses a global public health threat, causing over 1.3 million deaths worldwide. In the United States, there are more than 2.8 million cases of antimicrobial-resistant infections annually, resulting in over 35,000 deaths, according to the CDC's 2019 Antibiotic Resistance Threats Report.

Preventing antibiotic resistance

Cedars Sinai shares that using antibiotics correctly is the most effective way to prevent antibiotic resistance. Here are some key steps:

  • Don't take antibiotics for viral infections

  • Avoid saving antibiotics for future illnesses

  • Follow the prescription precisely, don't skip doses and complete the full treatment even if you feel better

  • Never take someone else's prescribed antibiotics

Health care providers can contribute by prescribing antibiotics only when necessary, using the right antibiotic for a specific bacteria, and prescribing the drugs for the required duration.


Cedars Sinai: Antibiotic Resistance

Centers for Disease Control and Prevention (CDC): Antibiotic Use Questions and Answers

Centers for Disease Control and Prevention (CDC): Antibiotics Aren’t Always the Answer

Cleveland Clinic: Antibiotics

Mayo Clinic: What Are the Effects of Drinking Alcohol While Taking Antibiotics?

Microbiology Society: What Are Antibiotics and How Do They Work?

National Health Service (myHSN): What are the 10 Most Common Antibiotics?

NHS Inform: Antibiotics

What This Means For You

Antibiotics can save lives, but they need to be used with care to avoid antibiotic resistance. Here, experts give you a primer on what they are and how they should be used.

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