Skip to Content

Antibiotics Guide

Medically reviewed on Aug 23, 2016 by L. Anderson, PharmD

You’ve most likely taken an antibiotic at least once in your lifetime. From treatments for painful strep throat or ear infections as a child, to burning urinary tract infections or itchy skin infections as an adult, antibiotics are one of the most highly utilized and important medication classes we have in medicine.

Understanding the vast world of antibiotics and anti-infectives is no easy task. Anti-infectives are a large class of drugs that cover a broad range of infections, including fungal, viral, bacterial, and even protozoal infections. Athletes foot? That’s a common fungal infection. HIV? Antiviral medications are always needed. Bladder infection? Yes, that may need a common antibiotic. And head lice? A topical anti-parasitic can alleviate the itching. There is no one type of antibiotic that cures every infection. Antibiotics specifically treat infections caused by bacteria, such as Staph., Strep., or E. coli., and either kill the bacteria (bactericidal) or keep it from reproducing and growing (bacteriostatic). Antibiotics do not work against any viral infection.

When To Use Antibiotics

Antibiotics are specific for the type of bacteria being treated and, in general, cannot be interchanged from one infection to another. When antibiotics are used correctly, they are usually safe with few side effects.

However, as with most drugs, antibiotics can lead to side effects that may range from being a nuisance to serious or life-threatening. In infants and the elderly, in patients with kidney or liver disease, in pregnant or breastfeeding women, and in many other patient groups antibiotic doses may need to be adjusted based upon the specific characteristics of the patient, like kidney or liver function, weight, or age. Drug interactions can also be common with antibiotics. Health care providers are able to assess each patient individually to determine the correct antibiotic and dose.

When NOT To Use Antibiotics

Antibiotics are not the correct choice for all infections. For example, most sore throats, cough and colds, flu or acute sinusitis are viral in origin (not bacterial) and do not need an antibiotic. These viral infections are “self-limiting”, meaning that your own immune system will usually kick in and fight the virus off. In fact, using antibiotics for viral infections can increase the risk for antibiotic resistance, lower the options for future treatments if an antibiotic is needed, and put a patient at risk for side effects and extra cost due to unnecessary drug treatment.

Antibiotic resistant bacteria cannot be fully inhibited or killed by an antibiotic, even though the antibiotic may have worked effectively before the resistance occurred. Don't share your antibiotic or take medicine that was prescribed for someone else, and don't save an antibiotic to use the next time you get sick.

To better understand antibiotics, it’s best to break them down into the most common infections, most common antibiotics, and the top antibiotic classes:

Top 10 List of Most Common Infections Treated with Antibiotics:

  1. Acne
  2. Bronchitis
  3. Conjunctivitis (Pink Eye)
  4. Otitis Media (Ear Infection)
  5. Sexually Transmitted Diseases (STD’s)
  6. Skin or Soft Tissue Infection
  7. Streptococcal Pharyngitis (Strep Throat)
  8. Traveler’s diarrhea
  9. Upper Respiratory Tract Infection
  10. Urinary Tract Infection (UTI)

Top 10 List of Generic Antibiotics:

  1. amoxicillin
  2. doxycycline
  3. cephalexin
  4. ciprofloxacin
  5. clindamycin
  6. metronidazole
  7. azithromycin
  8. sulfamethoxazole/trimethoprim
  9. amoxicillin/clavulanate
  10. levofloxacin

Top 10 List of Brand Name Antibiotics:

  1. Augmentin
  2. Flagyl, Flagyl ER
  3. Amoxil
  4. Cipro
  5. Keflex
  6. Bactrim, Bactrim DS
  7. Levaquin
  8. Zithromax
  9. Avelox
  10. Cleocin

Top 10 List of Antibiotic Classes (Types of Antibiotics):

  1. Penicillins
  2. Tetracyclines
  3. Cephalosporins
  4. Quinolones
  5. Lincomycins
  6. Macrolides
  7. Sulfonamides
  8. Glycopeptides
  9. Aminoglycosides
  10. Carbapenems

Most antibiotics fall into their individual antibiotic classes. An antibiotic class is a grouping of different drugs that have similar chemical and pharmacologic properties. Their chemical structures may look comparable, and drugs within the same class may kill the same or related bacteria.

However, it is important not to use an antibiotic for an infection unless your doctor specifically prescribes it, even if it's in the same class as another drug you were previously prescribed. Antibiotics are specific for the kind of bacteria they kill. Plus, you would need a full treatment regimen to effectively cure your infection, so don't use or give away leftover antibiotics.

1. Penicillins

Another name for this class is the beta-lactam antibiotics, referring to their structural formula. The penicillin class contains five groups of antibiotics: aminopenicillins, antipseudomonal penicillins, beta-lactamase inhibitors, natural penicillins, and the penicillinase resistant penicillins. Common antibiotics in the penicillin class include:

  • penicillin V potassium
  • amoxicillin
  • amoxicillin/clavulanate (Augmentin)

View penicillin drugs

2. Tetracyclines

Tetracyclines are broad-spectrum against many bacteria and treat conditions such as acne, urinary tract infections (UTIs), intestinal tract infections, eye infections, sexually transmitted diseases, periodontitis (gum disease), and other bacterial infections. The tetracycline class contains well-known drugs such as:

  • doxycycline
  • tetracycline
  • minocycline

View Tetracycline drugs

3. Cephalosporins

There are five generations of cephalosporins, with increasing expanded coverage to include gram-negative infections. Cephalosporins treat many infections, including strep throat, ear infections, urinary tract infections, skin infections, and meningitis. The fifth generation cephalosporin ceftaroline (Teflaro) is active against methicillin-resistant Staphylococcus aureus (MRSA). You’ve probably heard of common medications in this class, like:

  • cefuroxime (Ceftin)
  • ceftriaxone (Rocephin)
  • Cefdinir (Omnicef)

View cephalosporin drugs

4. Quinolones

The quinolones, also known as the fluoroquinolones, are a synthetic, bactericidal antibacterial class with a broad-spectrum of activity. The quinolones can be used for difficult-to-treat urinary tract infections when other options are aren’t effective, hospital-acquired pneumonia, bacterial prostatitis, and even anthrax or plague. The FDA issued a strong warning about this class in 2016. Familiar names in the fluoroquinolone class include:

  • ciprofloxacin (Cipro)
  • levofloxacin (Levaquin)
  • moxifloxacin (Avelox)

View quinolone drugs

5. Lincomycins

This class has activity against gram-positive aerobes and anaerobes (bacteria that can live without oxygen), as well as some gram-negative anaerobes. The lincomycin derivatives may be used to treat serious infections like pelvic inflammatory disease, intra-abdominal infections, lower respiratory tract infections, and bone and joint infections. These drugs include:

  • clindamycin (Cleocin)
  • lincomycin (Lincocin)

View lincomycin drugs

6. Macrolides

The macrolides can be use to treat community-acquired pneumonia, pertussis (whooping cough), or for uncomplicated skin infections, among other susceptible infections. Ketolides are a newer generation of antibiotic developed to overcome macrolide bacterial resistance. Frequently prescribed macrolides are:

  • azithromycin (Zithromax)
  • clarithromycin (Biaxin)
  • erythromycin

View macrolide drugs

7. Sulfonamides

Sulfonamides are effective against some gram-positive and many gram-negative bacteria, but resistance is widespread. Common uses for sulfonamides include UTIs, treatment or prevention of pneumocystis pneumonia, or ear infections (otitis media). Familiar names include:

  • sulfamethoxazole-trimethoprim (Bactrim, Bactrim DS, Septra)
  • sulfasalazine (Azulfidine)
  • sulfisoxazole (combined with erythromycin)

View sulfonamides drugs

8. Glycopeptide Antibiotics

Members of this group may be used for treating methicillin-resistant staphylococcus aureus (MRSA) infections, complicated skin infections, C. difficile-associated diarrhea, and enterococcal infections such as endocarditis which are resistant to beta-lactams and other antibiotics. Common drug names include:

  • dalbavancin (Dalvance)
  • oritavancin (Orbactiv)
  • telavancin (Vibativ)
  • vancomycin (Vancocin)

View glycopeptide drugs

9. Aminoglycosides

Aminoglycosides inhibit bacterial synthesis by binding to the 30S ribosome and act rapidly as bactericidal antibiotics (killing the bacteria). These drugs are usually given intravenously (in a vein through a needle). Common examples in this class are:

  • gentamicin
  • tobramycin
  • amikacin

View aminoglycoside drugs

10. Carbapenems

These injectable beta-lactam antibiotics have a wide spectrum of bacteria-killing power and may be used for moderate to life-threatening bacterial infections like stomach infections, pneumonias, kidney infections, multidrug-resistant hospital-acquired infections and many other types of serious bacterial illnesses. Members of this class include:

  • imipenem/cilastatin (Primaxin)
  • meropenem (Merrem)
  • doripenem (Doribax)
  • ertapenem (Inanz)

View carbapenems drugs

Are There Any Over-the-Counter Antibiotics?

Over-the-counter (OTC) oral antibiotics are not approved in the U.S. A bacterial infection is best treated with a prescription antibiotic that is specific for the type of bacteria causing the infection. This will increase the chances that the infection is cured and help to prevent antibiotic resistance. In addition, a lab culture may need to be performed to pinpoint the bacteria and to help select the best antibiotic. Taking the wrong antibiotic -- or not enough -- may worsen the infection and prevent the antibiotic from working the next time.

There are a few OTC topical antibiotics that can be used on the skin. Some products treat or prevent minor cuts, scrapes or burn on the skin that may get infected with bacteria. These are available in creams, ointments, and even sprays.

Common OTC topical antibiotics:

  • Neosporin, Medi-Quik (bacitracin/neomycin/polymyxin B)
  • Polysporin (bacitracin/polymyxin)
  • Triple antibiotic, generic (bacitracin/neomycin/polymyxin B)
  • Neosporin Plus (neomycin/polymyxin/pramoxine)

There are some OTC antibacterials for acne sufferers, too. They contain the antibacterial benzoyl peroxide, which also has mild drying effect for acne. Many products are found on the pharmacy shelves as gels, lotions, solutions, foams, cleaning pads, and even facial scrubs.

Common OTC antibacterials for acne:

  • Clearskin
  • Oxy-10
  • Proactiv

Need-to-Know: Trending Antibiotic Articles

Patients frequently have questions about specific topics with antibiotics. Here are some articles that address common questions you may have about antibiotics.

See Also:

Recommended for you