Cephalosporins are one of the most widely prescribed classes of medications in the world. Chances are you have encountered theseantibioticseven if you are unfamiliar with the name. For example, among other things, cephalexin is used to treatskin infectionsand infections of the bone, respiratory tract, urinary tract, and middle ear. Additionally, ceftriaxone is used to treatpneumonia.
Getty Images
What Are Cephalosporins?
Cephalosporins were first discovered in sewer water off the coast of Sardinia in 1945. By 1964, the first cephalosporin was prescribed.
Cephalosporins are structurally similar to other antibiotics. Like penicillins, cephalosporins have a beta-lactam ring attached to a dihyrdothiazole ring. Hanging off this dihyrdothiazole ring are various side chains, the composition of which makes for different cephalosporins with different pharmacology and antimicrobial activity.
Cephalosporins have three different mechanisms of action. They are:
Cephalosporins are divided into five generations. However, different cephalosporins in the same generation are sometimes chemically unrelated and have different spectra of activity (think cephamycins).
A generalization taught to many healthcare professionals is that with subsequent generations of cephalosporins,gram-positivecoverage decreases while gram-negative coverage increases.
One to 3% of all people are allergic to cephalosporins. In reality, however, this number is probably higher because people with penicillin allergies areoften not prescribed cephalosporins.
First-Generation Cephalosporins
First-generation cephalosporins come in oral and intravenous forms. They are active against Viridans streptococci, group A hemolytic streptococci, Staphylococcus aureus,E. coli, Klebsiella and Proteus bacteria. Like all other cephalosporins, first-generation cephalosporins don’t work on enterococci.
Examples of first-generation cephalosporins include the following:
In general, first-generation cephalosporins can be used to fight skin and other soft-tissue infections, respiratory tract infections, and urinary tract infections.Intravenous first-generation cephalosporins can be used as prophylaxis after clean surgical procedures.
The prevalence ofMRSAhas diminished the efficacy of first-generation cephalosporins as a means of prophylaxis and treatment.
Second-Generation Cephalosporins
In general, second-generation cephalosporins are more active against gram-negative organisms, making them more useful in many clinical situations.
For example, second-generation cephalosporins are active against strains of Proteus and Klebsiella. Second-generation cephalosporins also combat H. influenza—a cause of pneumonia, sepsis, and meningitis. Nevertheless, first-generation cephalosporins are generally still better at treating gram-positive infections.
Examples of second-generation cephalosporins include the following:
Second-generation cephalosporins treat the following:
Second-generation cephalosporins have no activity against Pseudomonas aeruginosa.
Third-Generation Cephalosporins
A major advantage of third- and fourth-generation antibiotics is significantly expanded coverage against gram-negative bacteria. Furthermore, the third-generation cephalosporin ceftazidime is active againstPseudomonas aeruginosa, a bacteria that can cause skin infections in people with normal immune systems (such as after exposure to an under-chlorinated hot tub or pool) as well as pneumonia, blood infections, and so forth in those with weakened immune systems. P. aeruginosa most commonly occurs in patients who have been hospitalized one week or longer). The infections can be highly complicated and life-threatening.
Ceftazidime also can be used as part of a combination therapy with avibactam when treatingP. aeruginosa.Its combination use in treating carbapenemase-producingEnterobacteriaceae(CPE) infections (like OXA-48) remains under study.
There are several third-generation cephalosporins. Discussing them all would be outside the scope of this article. Let’s instead focus on ceftriaxone which has numerous uses, including:
Fourth-Generation Cephalosporin
Cefepime is the only available (FDA-approved) fourth-generation cephalosporin. Like the third-generation cephalosporin ceftazidime, cefepime is active against Pseudomonas aeruginosa. Furthermore, cefepime is more active against Enterobacter and Citrobacterr bacteria. Finally, cefepime has gram-positive coverage comparable with ceftriaxone.
Here are some clinical uses for cefepime:
Fifth-Generation Cephalosporin
In 2010, the FDA approved Teflaro (ceftaroline), a fifth- or advanced-generation cephalosporin. Like cefepime, ceftaroline is a potent antibiotic that should be reserved for serious infection.
Specifically, it’s active against multidrug-resistant infections like MRSA (methicillin-resistantS. aureus) and VRSA (vancomycin-resistantS. aureus). This drug is also injectable and prescribed to fight community-acquired pneumonia and serious skin and soft tissue infections.
Ceftaroline is considered safe and effective but some infections do show resistance with its use.
A Word From Verywell
As you can now appreciate, cephalosporins are a remarkably diverse class of antibiotics with broad coverage. However, as with most antibiotics,antibiotic resistanceis a concern for many clinicians, epidemiologists, public health officials, and patients.
Bacterial resistance is partially due to physicians' overprescription; nevertheless, we can also help combat the development of resistance. For example, you shouldn’t always expect or demand that your prescriber gives you antibiotics to treat an infection which may very well be viral in nature. (Antibiotics are ineffective against viruses.) Furthermore, when prescribed antibiotics, it’s imperative that you finish the entire course even if you “feel better.”
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Abraham EP.Cephalosporins 1945-1986. Drugs. 1987;34 Suppl 2:1-14.doi:10.2165/00003495-198700342-00003
Kapoor G, Saigal S, Elongavan A.Action and resistance mechanisms of antibiotics: A guide for clinicians.J Anaesthesiol Clin Pharmacol. 2017;33(3):300–305. doi:10.4103/joacp.JOACP_349_15
Kwak YG, Choi SH, Kim T, et al.Clinical Guidelines for the Antibiotic Treatment for Community-Acquired Skin and Soft Tissue Infection.Infect Chemother. 2017;49(4):301–325. doi:10.3947/ic.2017.49.4.301
Onorato L, Di Caprio G, Signoriello S, Coppola N.Efficacy of ceftazidime/avibactam in monotherapy or combination therapy against carbapenem-resistant Gram-negative bacteria: A meta-analysis.Int J Antimicrob Agents. 2019 Dec;54(6):735-740. doi:10.1016/j.ijantimicag.2019.08.025.
Cilloniz C, Pericàs JM, Rojas J.Ceftaroline in severe community-acquired pneumonia.Rev Esp Quimioter. 2022 Apr;35 Suppl 1(Suppl 1):28-30. doi:10.37201/req/s01.06.2022.
Silva JT, López-Medrano F.Cefiderocol, a new antibiotic against multidrug-resistant Gram-negative bacteria.Rev Esp Quimioter.2021 Sep;34 Suppl 1(Suppl1):41-43. doi:10.37201/req/s01.12.2021.
Dickson SD, Salazar KC.Diagnosis and management of immediate hypersensitivity reactions to cephalosporins.Clin Rev Allergy Immunol. 2013;45(1):131-42. doi:10.1007/s12016-013-8367-xPowers JH. “Use and Importance of Cephalosporins in Human Medicine” Presentation. FDA.Guglielmo B. Anti-Infective Chemotherapeutic & Antibiotic Agents. In: Papadakis MA, McPhee SJ, Rabow MW. eds.Current Medical Diagnosis & Treatment 2015.New York, NY: McGraw-Hill
Dickson SD, Salazar KC.Diagnosis and management of immediate hypersensitivity reactions to cephalosporins.Clin Rev Allergy Immunol. 2013;45(1):131-42. doi:10.1007/s12016-013-8367-x
Powers JH. “Use and Importance of Cephalosporins in Human Medicine” Presentation. FDA.
Meet Our Medical Expert Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?OtherHelpfulReport an ErrorSubmit
What is your feedback?
