Types Of Antibiotics, Uses, classes, Resistance and Side Effects

Types antibiotics

Overview

Antibiotics are important drugs. Many antibiotics can successfully treat infections caused by bacteria (bacterial infections). Antibiotics can prevent the spread of disease. And antibiotics can reduce serious disease complications.

But some antibiotics that used to be typical treatments for bacterial infections now don't work as well. And some drugs don't work at all against some bacteria. When an antibiotic no longer works against some strains of bacteria, those bacteria are said to be antibiotic resistant. Antibiotic resistance is one of the world's most urgent health problems.

Understanding the vast world of antibiotics and anti-infectives is no easy task. Anti-infectives are a larger class of many types of drugs that cover a broad range of infections, including antibiotics, antifungals, antiviral, and even protozoal infections.

Examples

  • Athletes foot: That’s a common fungal infection.
  • HIV: Antiviral medications are always needed.
  • Bladder infection: Yes, that may need a common oral antibiotic.
  • 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. Health care providers are able to assess each patient individually to determine the correct antibiotic, dose and length of treatment.

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 individual patient. Drug interactions can also be common with antibiotics. 

When NOT To Use Antibiotics

Antibiotics are not the correct choice for all infections. For example, most sore throats, cough and colds, flu, COVID 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.

Using antibiotics for viral infections can increase the risk for antibiotic resistance. Antibiotic-resistant bacteria cannot be fully inhibited or killed by an antibiotic, even though the antibiotic may have worked effectively before the resistance occurred.  This can also lower your options for effective treatments if an antibiotic is needed eventually due to a secondary infection. Using unnecessary antibiotics also puts you at risk for side effects and adds extra cost.

It's important not to 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. It may not be the right drug for your illness.

To better understand antibiotics, it’s best to break them down into common infections, common antibiotics, and the top antibiotic classes as listed in Drugs.com.

Top 10 List of 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 and trimethoprim
  9. amoxicillin and 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.

Note: Tables below are not all-inclusive, generics are available for many brands.

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: aminopenicillinsantipseudomonal penicillinsbeta-lactamase inhibitorsnatural penicillins, and the penicillinase resistant penicillins.

Common antibiotics in the penicillin class include:

GenericBrand Name Examples

amoxicillin

Amoxil
amoxicillin and clavulanateAugmentin, Augmentin ES-600
ampicillinUnasyn
dicloxacillinN/A
oxacillinBactocill
penicillin V potassiumPenicillin VK

Certain penicillinase-resistant penicillins (such as oxacillin or dicloxacillin) are inherently resistant to certain beta-lactamase enzymes by themselves. Others, for example, amoxicillin or ampicillin have greater antibacterial activity when they are combined with a beta-lactamase inhibitor like clavulanate, sulbactam, or tazobactam.

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 drugs such as:

GenericBrand Name Examples

demeclocycline

N/A

doxycycline

DoryxDoxy 100MonodoxOraceaVibramycin
eravacyclineXerava
minocyclineAmzeeqDynacinMinocin, Minolira, Solodyn, Ximino, Zilxi

omadacycline

Nuzyra

sarecycline

Seysara
tetracycline Achromycin V

3. Cephalosporins

There are five generations of cephalosporins, with increasing expanded coverage across the class to include gram-negative infections. Newer generations with updated structures are developed to allow wider coverage of certain bacteria. Cephalosporins are bactericidal (kill bacteria) and work in a similar way as the penicillins.

Cephalosporins treat many types of infections, including strep throat, ear infections, urinary tract infections, skin infections, lung infections, and meningitis. Common medications in this class include:

GenericBrand Name ExamplesGeneration
cefaclorN/A2nd generation
cefadroxilDuricef1st generation
cefdinirN/A3rd generation
cephalexinKeflex1st generation
cefprozilCefzil2nd generation
cefdinirN/A3rd generation
cefepimeMaxipime4th generation
cefiderocolFetroja4th generation
cefotaximeN/A3rd generation
cefotetanCefotan2nd generation
ceftarolineTeflaro5th (next) generation
ceftazidimeAvycazFortazTazicef3rd generation
ceftriaxoneN/A3rd generation
cefuroximeCeftinZinacef2nd generation 

The fifth generation (or next generation) cephalosporin known as ceftaroline (Teflaro) is active against methicillin-resistant Staphylococcus aureus (MRSA). Avycaz contains the the beta-lactamase inhibitor avibactam. 

4. Fluoroquinolones

The fluoroquinolones, also known as the quinolones, are a synthetic, bactericidal antibacterial class with a broad-spectrum of activity used in adults (not children). Due to risk of multiple serious side effects, the FDA has advised that they are not suitable for common infections such as sinusitis, bronchitis, and uncomplicated urinary tract infections. They should only be considered when treatment with other, less toxic antibiotics, has failed. Ask your doctor about the warnings associated with this class of drug before you take it.

The FDA has issued several strong warnings about this class due to potential disabling side effects. Learn More: FDA Drug Safety Communication: FDA updates warnings for oral and injectable fluoroquinolone antibiotics due to disabling side effects

Common drugs in the fluoroquinolone class include:

GenericBrand Name Examples
ciprofloxacinCipro, Cipro XR
delafloxacinBaxdela
levofloxacinN/A
moxifloxacinAvelox
gemifloxacinFactive

Several fluoroquinolones are also available in drop form to treat eye or ear infections.

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. Some forms are also used topically on the skin to treat acne. A single-dose vaginal cream is also available to treat certain bacterial vaginal infections (bacterial vaginosis). These drugs include:

GenericBrand Name Examples
clindamycinCleocinCleocin TClindetsClindesseEvoclin
lincomycinLincocin

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:

GenericBrand Name Examples
azithromycinZithromax
clarithromycinBiaxin
erythromycinE.E.S.Ery-TabEryc 
fidaxomicin (ketolide)Dificid

7. Sulfonamides

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

GenericBrand Name Examples
sulfamethoxazole and trimethoprim

BactrimBactrim DSSeptra

sulfasalazineAzulfidine

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:

GenericBrand Name Examples
dalbavancinDalvance
oritavancinOrbactivKimyrsa
telavancinVibativ
vancomycinFirvanqVancocin

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); inhaled and ophthalmic (eye) dose forms are also available. Examples in this class are:

GenericBrand Name Examples

gentamicin

GenopticGentak
tobramycinAktobKitabis PakTOBITobrex
amikacinAmikinArikayce

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. They are often saved for more serious infections or used as "last-line" agents to help prevent resistance. Members of this class include:

GenericBrand Name Examples
imipenem and cilastatinPrimaxinRecarbrio
meropenemMerrem Vabomere
ertapenemInvanz

Note: Recarbrio is a combination medicine that contains imipenem, cilastatin and the beta-lactamse inhibitor relebactam. Vabomere is a combination product that contains meropenem and the beta-lactamse inhibitor vaborbactam.

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. Using a specific antibiotic 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 over-the-counter topical antibiotics that can be used on the skin. Some products treat or prevent minor cuts, scrapes or burns on the skin that may get infected with bacteria. These are available in creams, ointments, and even sprays.

Common OTC topical antibiotics:

  • Neosporin (bacitracin, neomycin, polymyxin B)
  • Polysporin (bacitracin, polymyxin B)
  • Triple antibiotic, generic (bacitracin, neomycin, polymyxin B)
  • Neosporin + Pain Relief Ointment (bacitracin, neomycin, polymyxin B, pramoxine)

There are some OTC antibacterials for treating acne, 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.

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