They work to clear up infections either by killing bacteria or stopping their growth.
Antibiotics typically have to be prescribed by a healthcare provider.
Antibiotics are divided into several classes based on how they work and what kinds of conditions they treat.
katleho Seisa / Getty Images
Penicillins include the following medications:
Penicillins are usually taken orally or by injection.
They might also be used in combination.
For example, a combination ofamoxicillin and clavulanateis commonly prescribed to treat infection.
Certain medications interact with penicillins, including aspirin, phenylbutazone, sulfonamides, and others.
Be sure to discuss your current medications with your healthcare provider before taking this antibiotic.
Penicillins may also reduce the effectiveness of oral contraceptives.
Penicillins are generally considered safe to use during pregnancy and breastfeeding.
There are several different generations of cephalosporins.
Each generation is effective at treating different types of infections.
Lincosamides
Lincosamidesare a class of antibiotics that include just two medications: lincomycin and clindamycin.
They are a narrow-spectrum antibacterial medication that is effective against gram-positive bacteria but not gram-negative bacteria.
Lincosamides might be used to treat certain gynecological infections, bone and joint infections, or lower abdominal infections.
Macrolides include:
Macrolides are sometimes used to treat streptococcal and pneumococcal infections when penicillin cannot be used.
Fluoroquinolones
Fluoroquinolonesare broad-spectrum, systemic antibacterial agents used to treat bacterial infections.
Sulfonamides
Sulfonamides include medication combinations such as trimethoprim-sulfamethoxazole that work together to treat bacterial infections.
These medications may be taken orally (by mouth), but some are available as topical medications.
Sulfonamides include the following medications:
Sulfonamides can be used to treat conditions including burns and vaginitis.
They may also be used for superficial ocular infections or inflammatory bowel disease.
In combination with other medications, they may also treat infections such as urinary tract infections.
Glycopeptides and Lipoglycopeptides
Glycopeptidesandlipoglycopeptidesare medications that are used to treat certain complicated or serious infections.
They work by work by preventing gram-positive bacteria from forming a cell wall, which kills the bacteria.
Tetracyclines
Tetracyclines are a group of broad-spectrum antibiotics used to treat a wide variety of bacterial infections.
Urinary Anti-Infectives
This class of antibiotics treats urinary tract infections (UTIs).
The first line of defense for a UTI is antibiotics.
Urinary anti-infectives include:
Many urinary tract infections (UTIs) go away on their own without antibiotics.
If your UTI symptoms persist or get worse, you should seek medical treatment.
You may start feeling better in just one to three days.
Antibiotic Allergy
Some people develop allergy symptoms after taking antibiotics.
Allergic reactions to penicillins are particularly commonan estimated 5% to 15% of people have a penicillin allergy.
Antibiotics During Pregnancy
There has been some concern regarding the use of sulfonamides and nitrofurantoin during pregnancy.
Certain other antibioticsfluoroquinolones and tetracyclinesshould be avoided if youre currently pregnant.
When Antibiotics Shouldn’t Be Used
It may be tempting to take antibiotics whenever youre sick.
Your healthcare provider can help you decide what treatment will be appropriate and effective for your infection.
Also, antibiotics only work to fight certain bacterial infections.
They arent effective in treating all conditions resulting from bacteria, including some ear infections and most sinus infections.
Antibiotic Resistance
Antibiotic-resistant infections may occur when antibiotics arent able to kill off certain bacteria.
Antibiotic resistance can cause serious health complications, such as organ failure.
In some cases, it may even be fatal.
There are over 2.8 million antibiotic-resistant infections in the U.S. each year, resulting in over 35,000 deaths.
You may be more likely to develop an antibiotic-resistant infection if you take antibiotics too often or unnecessarily.
Only take antibiotics when you need them.
Your options may include over-the-counter antibiotics or natural antibiotics.
Discuss any antibiotic alternative with your provider to be sure that your infection is managed properly.
OTC Antibiotics
Most of the time, antibiotics need to be prescribed by a healthcare provider.
However, some over-the-counter (OTC) topical antibiotic treatments are available at pharmacies and drugstores.
Neosporin is only effective in treating minor skin injuries.
Natural Antibiotics
There are some natural substances that have antimicrobial properties.
Examples of common antibiotics include penicillin, azithromycin, clindamycin, and cephalexin.
Antibiotics cant treat infections brought on by viruses, including colds, flu, and runny noses.
Its important to take antibiotics exactly as your healthcare provider prescribes.
If you take antibiotics too often, you’re free to develop antibiotic-resistant infections.
Centers for Disease Control and Prevention.Antibiotic use questions and answers.
Dallo M, Patel K, Hebert A.Topical antibiotic treatment in dermatology.Antibiotics (Basel).
2023 Feb;12(2):188. doi:10.3390/antibiotics12020188
Centers for Disease Control and Prevention.Antibiotic class definitions.
Merck Manual.Penicillins
Yip DW, Gerriets V.Penicillin.
In: StatPearls [Internet].
2019 Nov 15;100(10):599-600.
PMID: 31730323
Merck Manual.Cephalosporins
Taylor & Francis.
Knowledge Base.Lincosamides
Murphy PB, Bistas KG, Patel P, et al.Clindamycin.
In: StatPearls [Internet].
Treasure Island (FL): StatPearls Publishing; 2025
ScienceDirect.Roxithromycin
Merck Manual.Macrolides
Durham Region Health Department.
2020;70(699):e714-e722.
doi:10.3399/bjgp20X712781
American Journal of Managed Care.What pop in of medication can an urgent care doctor prescribe?
Centers for Disease Control and Prevention.Antibiotic do’s and don’ts.
Rezaei N, Bazzazi A, Naseri Alavi S.Neurotoxicity of the antibiotics: A comprehensive study.Neurol India.
2015;35(11):1052-1062. doi:10.1002/phar.1649
Centers for Disease Control and Prevention.About antibiotic resistance.
Neosporin.Neosporin + Pain Relief Cream.
2021 Sep 6;12:723233. doi:10.3389/fphar.2021.723233