Cephalosporins are a type of antibiotic that can treat a range of simple infections. People can take them orally or doctors can inject them into a vein.

Cephalosporins are a type of antibiotic. Antibiotics are medications that treat bacterial infections. There are many types, often called classes, of antibiotics available. Cephalosporins are a type of beta-lactam antibiotic.

They can be taken orally or injected into a vein (intravenous injection), depending on the infection.

Read on to learn more about cephalosporins, including what they treat and the side effects they can cause.

Healthcare providers use cephalosporins to treat a variety of bacterial infections, especially for people who are allergic to penicillin, another common antibiotic.

Some examples of infections that cephalosporins can treat include:

Oral cephalosporins are generally used for simple infections that are easy to treat. For example, a routine case of strep throat might be treated with a course of oral cephalosporins.

Intravenous (IV) cephalosporins are used for more severe infections. This is because IV antibiotics reach your tissues faster, which can make a big difference if you have a serious infection, such as meningitis.

Cephalosporins are grouped together based on the type of bacteria that they’re most effective against. These groups are referred to as generations. There are five generations of cephalosporins.

To understand the differences between the generations, it’s important to understand the difference between Gram-positive and Gram-negative bacteria.

One of the main distinctions between the two is their cell wall structure:

  • Gram-positive bacteria have thicker membranes that are easier to penetrate. Think of their cell wall as a chunky, loose-knit sweater.
  • Gram-negative bacteria have thinner membranes that are harder to penetrate, making them more resistant to some antibiotics. Think of their wall as a piece of fine chain mail.

First-generation cephalosporins

First-generation cephalosporins are very effective against Gram-positive bacteria. But they’re only somewhat effective against Gram-negative bacteria.

First-generation cephalosporins might be used to treat:

  • skin and soft tissue infections
  • UTIS
  • strep throat
  • ear infections
  • pneumonia

Some first-generation cephalosporins are used as prophylactic antibiotics for surgery involving the chest, abdomen, or pelvis.

Examples of first-generation cephalosporins include:

  • cephalexin (Keflex)
  • cefadroxil (Duricef)
  • cephradine (Velosef)

First-generation cephalosporins are more effective against Gram-positive bacteria, though they also work against some Gram-negative bacteria.

Second-generation cephalosporins

Second-generation cephalosporins also target some types of Gram-positive and Gram-negative bacteria. But they’re less effective against certain Gram-positive bacteria than first-generation cephalosporins are.

They’re often used to treat respiratory infections, such as bronchitis or pneumonia.

Other infections sometimes treated with second-generation cephalosporins include:

Examples of second-generation cephalosporins include:


Second-generation cephalosporins target both Gram-positive and Gram-negative bacteria. But they’re a little less effective against Gram-positive bacteria compared to first-generation cephalosporins

Third-generation cephalosporins

Third-generation cephalosporins are more effective against Gram-negative bacteria compared to both the first and second generations. They’re also more active against bacteria that may be resistant to previous generations of cephalosporins.

The third generation also tend to be less active than previous generations against Gram-positive bacteria, including Streptococcus and Staphylococcus species.

One third-generation cephalosporin, ceftazidime (Fortaz), is often used to treat pseudomonas infections, including hot tub folliculitis.

Third-generation cephalosporins may also be used to treat:

  • skin and soft tissue infections
  • pneumonia
  • UTIs
  • gonorrhea
  • menigitis
  • Lyme disease
  • sepsis

A few examples of third-generation cephalosporins include:

  • cefixime (Suprax)
  • ceftibuten (Cedax)
  • cefpodoxime (Vantin)

Third-generation cephalosporins are effective against many Gram-negative bacteria and bacteria that haven’t responded to first- or second-generation cephalosporins.

Fourth-generation cephalosporins

Cefepime (Maxipime) is the only fourth-generation cephalosporin that’s available in the United States. While effective against a variety of Gram-positive and Gram-negative bacteria, it’s usually reserved for more severe infections.

Cefepime can be used to treat the following types of infections:

  • skin and soft tissue infections
  • pneumonia
  • UTIs
  • abdominal infections
  • meningitis
  • sepsis

Cefepime can be administered intravenously or with an intramuscular injection. It may also be given to people with a low white blood cell count, which can increase the risk of developing a severe infection.


Fourth-generation cephalosporins work against both Gram-positive and Gram-negative bacteria. They’re generally used for more severe infections or for those with weakened immune systems.

Fifth-generation cephalosporins

You may hear fifth-generation cephalosporins referred to as advanced- generation cephalosporins. There’s one fifth-generation cephalosporin, ceftaroline (Teflaro), available in the United States.

This cephalosporin can be used to treat bacteria, including resistant Staphylococcus aureus (MRSA) and Streptococcus species, that are resistant to penicillin antibiotics.

Otherwise, ceftaroline’s activity is similar to that of third-generation cephalosporins, although it isn’t effective against Pseudomonas aeruginosa.


Ceftaroline is the only fifth-generation cephalosporin available in the United States. It’s often used to treat infections, including MRSA infections, that are resistant to other antibiotics.

As with any kind of medication, you can be allergic to cephalosporins. The most common sign of an allergic reaction to cephalosproins is a skin rash.

In rare cases, cephalosprins may cause a serious allergic reaction known as anaphylaxis.

Symptoms of anaphylaxis include:

  • hives
  • flushed skin
  • swollen tongue and throat
  • breathing difficulties
  • low blood pressure
  • rapid or weak pulse
  • nausea or vomiting
  • diarrhea
  • dizziness
  • fainting
get help

Anaphylaxis can be life-threatening. Seek immediate medical treatment if you’re taking a cephalosporin and experience symptoms of anaphylaxis.

What if I’m allergic to penicillin?

It’s rare to be allergic to both penicillin and cephalosporins. But if you’ve had a serious anaphylactic reaction to penicillin antibiotics in the past, you shouldn’t take cephalosporins.

It’s uncommon to have an allergy to both penicillin antibiotics and cephalosporins, so cephalosporins can be used cautiously in people with a penicillin allergy.

However, people who’ve had a serious anaphylactic reaction to penicillin antibiotics shouldn’t take cephalosporins.

In addition, some cephalosporins are more likely to cause a reaction in people with a penicillin allergy. These include:

  • cephalothin
  • cephalexin
  • cefadroxil
  • cefazolin

Cephalosporins can cause a range of side effects, including:

  • stomach upset
  • nausea
  • vomiting
  • diarrhea
  • yeast infection or oral thrush
  • dizziness

One of the more serious side effects that can occur is a C. difficile infection. This infection typically occurs after a long course of antibiotics and can be potentially life-threatening.

Symptoms to watch out for include:

  • watery diarrhea
  • abdominal pain
  • fever
  • nausea
  • decreased appetite

You can help to prevent stomach upset and diarrhea by:

  • taking probiotics, which can help to add good bacteria to your digestive tract
  • following the instructions that come with your medication, as some antibiotics should be taken with food, while others should be taken on an empty stomach
  • avoiding foods that can contribute to stomach upset, such as spicy or greasy foods

Cephalosporins are generally safe for most people, including those who are pregnant. In fact, some first-generation cephalosporins are commonly used to treat UTIs in pregnant people.

However, you shouldn’t take cephalosporins if you’re breastfeeding.

Cephalosporins can sometimes interact with other medications you’re taking. Make sure to tell your healthcare provider about all other medications you take, including supplements, vitamins, and over-the-counter medications.

Cephalosporins are a type of antibiotic used to treat a range of bacterial infections. There are different generations of cephalosporins, and some are better suited to treat certain infections than others.

If you have to take antibiotics, make sure to tell your doctor about all other medications you take, as well as any previous allergic reactions to antibiotics.


Make sure you take the full course of antibiotics as prescribed by your doctor, even if you start to feel better before finishing them. Otherwise, you may not kill all of the bacteria, which can make them resistant to antibiotics.