Antibiotics 101

Taking Antibiotics

You’ve most likely taken an antibiotic or anti-infective 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 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

Types of Antibiotics

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.

Top 10 List of Antibiotic Classes

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

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: aminopenicillins, antipseudomonal penicillins, beta-lactamase inhibitors, natural penicillins, and the penicillinase resistant penicillins.

Common antibiotics in the penicillin class include:

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:

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:

The fifth generation (or next generation) cephalosporin known as ceftaroline (Teflaro) is active against methicillin-resistant Staphylococcus aureus (MRSA). It is also active against Listeria monocytogenes and Enterococcus faecalis, but ceftaroline does not cover Pseudomonas aeruginosa. 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:

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:

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. Fidaxomicin is used to treat Clostridium difficile-associated diarrhea. Frequently prescribed macrolides include:

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:

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, pneumonia in a hospital setting, and enterococcal infections such as endocarditis which are resistant to beta-lactams and other antibiotics. Common drug names include:

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:

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:

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.

Common OTC antibacterials for acne:

• Clearskin
• Oxy-10
• Proactiv