Antibiotics like amoxicillin are medicines that treat bacterial infections. Some antibiotics break down cell walls, while others inhibit protein production. This kills or prevents bacteria from reproducing and spreading.

Oral antibiotics are available in liquid, tablet, and capsule form. Topical antibiotics include skin creams, sprays, and ointments. Eye ointments, eye drops, and ear drops are also available. Severe infections may require injected or intravenous antibiotics.

Healthcare professionals prescribe different antibiotics to treat conditions such as strep throat, bronchitis, and inner ear infections. In this case, these infections are moderate to severe and have not improved with other treatments.

Antibiotics do not treat viral illnesses, such as a cold, the flu, or mono.

These drugs are grouped according to their antibacterial activity and chemical structure. Specific antibiotics fight certain bacteria, which makes it important to take the right kind. A healthcare professional may ask for a lab culture test to determine which antibiotics you need.

Read on to learn more about the most common types of antibiotics and which infections they treat. We also explore the common side effects of antibiotics, which can include gastrointestinal problems like nausea, vomiting, and diarrhea, as well as more serious effects.

Here are some types of antibiotics that doctors prescribe most often.


Penicillins are a common treatment for a variety of skin conditions. They also treat middle ear, kidney, and blood infections. Penicillin antibiotics are effective at killing Staphylococci and Streptococci infections. But some bacteria are resistant to penicillin, due to overuse.

Common penicillin antibiotics include:

  • phenoxymethylpenicillin
  • dicloxacillin
  • amoxicillin with clavulanic acid
  • ampicillin
  • nafcillin
  • oxacillin
  • penicillin V
  • penicillin G

Potential side effects include:

  • nausea
  • abdominal discomfort
  • diarrhea
  • headache
  • yeast infection
  • liver disease

Penicillin may cause allergic reactions, such as rashes, hives, and breathing difficulties.

Some medications that may interact with penicillin include oral contraceptives and the anti-inflammatories aspirin and probenecid.


Cephalosporins often treat gonorrhea, pelvic inflammatory disease, and sinusitis. They also treat urinary tract infections (UTIs), epididymo-orchitis, and cellulitis. Often, doctors prescribe cephalosporins to people who are allergic to penicillin.

Common cephalosporin antibiotics include:

  • cefaclor
  • cefazolin
  • cefadroxil
  • cephalexin
  • cefuroxime
  • cefixime
  • cefoxitin
  • ceftriaxone


Tetracyclines are a group of antibiotics with anti-inflammatory properties that can treat several bacterial infections. They commonly treat chest, urethral, and pelvic infections. Tetracyclines also treat inflammatory skin conditions, such as acne, rosacea, and perioral dermatitis.

Common tetracycline antibiotics include:

  • doxycycline
  • minocycline
  • sarecycline

Children under 12 and pregnant or breastfeeding people should not take tetracyclines because they have the potential to stain developing teeth.

They can also cause inflammation or irritation of the esophagus. To prevent this, make sure to take doxycycline while sitting or standing upright, and have plenty of water. Also, it’s a good idea to avoid sun exposure, since doxycycline causes photosensitivity, which can lead to sunburn.

Finally, it’s best to take this type of antibiotic after eating to prevent nausea, vomiting, and diarrhea.

Minocycline has more potential side effects than doxycycline, though it’s less likely to cause photosensitivity. Possible adverse effects of minocycline include drug hypersensitivity syndrome, autoimmune reactions, and dizziness and headache. Also, using it for a long period may cause blue pigmentation of skin and nails.

Medications that may interact with tetracyclines include:

  • systemic retinoids, such as acitretin, isotretinoin, and alitretinoin
  • diuretics
  • lithium
  • anticonvulsants
  • rifampicin
  • celestipol
  • oral contraceptives


Macrolides are an antibiotic group with anti-inflammatory and immunomodulatory properties. They can treat strains of bacteria that are resistant to penicillin. They are also a suitable option for people who are allergic to penicillin or cephalosporin.

These antibiotics commonly treat skin, soft tissue, respiratory, and sexually transmitted infections, including chlamydia. Healthcare professionals use them, for example, to treat skin conditions like acne, rosacea, erythrasma, and pityriasis lichenoides.

Types of macrolides include:

  • erythromycin
  • clarithromycin
  • azithromycin
  • fidaxomicin
  • roxithromycin

Macrolides, especially erythromycin and clarithromycin, can adversely interact with certain medications. Reactions and toxicity are more common in older adults and people with renal or liver dysfunction.

Medications that may interact with macrolides include:

  • calcium channel blockers, such as verapamil
  • amiodarone
  • methadone
  • lithium
  • amitriptyline
  • citalopram
  • anticoagulants, including warfarin and dabigatran
  • digoxin
  • benzodiazepines
  • carbamazepine
  • cimetidine
  • clozapine
  • colchicine
  • theophylline


Fluoroquinolones, also called quinolones, can fight bacterial infections that are life threatening or challenging to treat. However, they are linked with antimicrobial resistance, so you shouldn’t take them unless it’s absolutely necessary.

Fluoroquinolones are the first-line treatment for prostatitis, along with severe cases of salmonellosis and shigellosis. Doctors also often use them to treat certain cases of epididymo-orchitis, gonorrhea, and tuberculosis. Sometimes, fluoroquinolones treat urinary, eye, and ear infections.

Types of fluoroquinolone include:

  • ciprofloxacin
  • ofloxacin
  • levofloxacin
  • moxifloxacin

For people with renal dysfunction, taking this type of drug may require adjustments to dosages of other medications. And, rarely, fluoroquinolone can cause serious adverse effects, especially in older adults.

Potential side effects include:

  • tendon rupture
  • aortic aneurysm rupture or dissection
  • aortic and mitral regurgitation
  • central nervous system excitation and seizures
  • QT prolongation
  • other cardiac conditions


Sulfonamides, also called sulfa drugs, are a type of synthetic antimicrobial that doctors prescribe when first-line treatments are ineffective or contraindicated. The most common type is sulfamethoxazole with trimethoprim, called co-trimoxazole. It treats conditions such as pneumocystis pneumonia and nocardiosis in people with weakened immunity, as well as infections of the lower urinary tract in children.

Types of sulfonamides include:

  • sulfamethoxazole with trimethoprim
  • sulfasalazine
  • sulfacetamide
  • sulfadiazine silver

Sulfonamides are unsafe during pregnancy because they increase the likelihood of pregnancy loss.

Potential side effects include:

Medications that may interact with sulfonamides include:


Glycopeptide antibiotics treat drug-resistant bacteria and gram-positive infections, including multidrug-resistant Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus, better known as MRSA.

Types of glycopeptides include:

  • vancomycin
  • dalbavancin
  • oritavancin
  • telavancin

Below, find answers to common questions about antibiotics.

What is antibiotic resistance?

Antibiotic resistance occurs when bacteria survive or resist antibiotic treatment. Bacteria change and mutate to protect themselves after coming into contact with an antibiotic or other bacteria. Once a type of bacteria is resistant, it passes these genes to other bacteria, which continue to grow. Eventually, they create a new strain of antibiotic-resistant bacteria.

Misusing and overusing antibiotics increases the likelihood of antibiotic resistance. Over time, this may lead to a shortage of medications that can effectively treat common infections.

How can I prevent antibiotic resistance?

To prevent antibiotic resistance, avoid taking antibiotics unless it is essential. Don’t take them for viral infections, such as a cold or the flu. Always follow the instructions from your healthcare professional about how much to take when. To prevent infections, clean your hands and living spaces regularly, and take steps to strengthen your immune system.

Are there any natural antibiotics?

Natural antibiotics include honey, thyme essential oil, and oregano essential oil. Extracts of garlic, cranberry, and myrrh also have antibiotic properties. Several herbs are effective antibiotics, including echinacea, turmeric, and ginger.

Natural UTI treatments include D-mannose and uva ursi, along with green, parsley, mint, and chamomile teas.

You can experiment with different combinations of natural treatments to find out which are most effective for your needs.

Antibiotics kill bacteria and prevent them from multiplying. They are valuable drugs that treat bacterial infections. It’s crucial to use them correctly and follow the healthcare professional’s instructions carefully.

It’s also important to be aware of the potential side effects and interactions of antibiotics. Speak with your doctor if you have any related concerns.