Skip to main content

First generation cephalosporins

Medically reviewed by Carmen Pope, BPharm. Last updated on April 13, 2023.

What are First generation cephalosporins?

After the first cephalosporin was discovered in 1945, scientists improved the structure of cephalosporins to make them more effective against a wider range of bacteria. Each time the structure changed, a new "generation" of cephalosporins were made. There are five generations of cephalosporins. First generation cephalosporins refer to the first group of cephalosporins discovered. Their optimum activity is against gram-positive bacteria such as staphylococci and streptococci. They have little activity against gram-negative bacteria.

Cephalosporins are a large group of antibiotics derived from the mold Acremonium (previously called Cephalosporium). Cephalosporins are bactericidal (kill bacteria) and work in a similar way to penicillins. They bind to and block the activity of enzymes responsible for making peptidoglycan, an important component of the bacterial cell wall. They are called broad-spectrum antibiotics because they are effective against a wide range of bacteria.

What are first generation cephalosporins used for?

First generation cephalosporins may be used to treat infections caused by susceptible bacteria such as:

  • Bone infections
  • Ear infections (eg, otitis media)
  • Skin infections
  • Upper respiratory tract infections
  • Urinary tract infections.

What are the differences between first generation cephalosporins?

Cephalexin and cefadroxil can be given by mouth, whereas cefazolin can only be given by injection (IV/IM). There are also differences with regards to how frequently the different first-generation cephalosporins need to be dosed.

Generic name Brand name examples
cefadroxil Duricef
cefazolin Ancef
cephadrine Discontinued
cephalexin Keflex

Are first generation cephalosporins safe?

First generation cephalosporins are generally safe, with low toxicity and good efficacy against susceptible bacteria.

Allergic reactions have been reported with cephalosporins (including first generation cephalosporins) and symptoms may include a rash, hives (urticaria), swelling, or rarely, anaphylaxis. Up to 10% of people with a history of penicillin allergy will also be allergic to cephalosporins.

Rarely, seizures have been reported with some cephalosporins; the risk is greatest in those with kidney disease.

Cephalosporins have also been associated with a reduced ability of the blood to clot leading to prolonged bleeding times. People with kidney or liver disease, nutritionally deprived, taking cephalosporins long-term, or concurrently receiving anticoagulant therapy are more at risk.

For a complete list of severe side effects, please refer to the individual drug monographs.

What are the side effects of first generation cephalosporins?

First generation cephalosporins generally cause few side effects. The most common side effects reported include diarrhea, nausea and vomiting, dyspepsia, gastritis and abdominal pain. Transient liver problems have also been reported.

Rarely, some people may develop a super-infection due to overgrowth of a naturally occurring bacterium called Clostridium difficile, following use of any antibiotic, including cephalosporins. Symptoms may include severe diarrhea.

Uncommonly, an overgrowth of the yeast, Candida albicans, may occur following cephalosporin use, resulting in the symptoms of thrush.

For a complete list of side effects, please refer to the individual drug monographs.

List of First generation cephalosporins

View by  Brand | Generic
Drug Name Avg. Rating Reviews
Keflex (Pro)
Generic name: cephalexin
88 reviews
Duricef (Pro)
Generic name: cefadroxil
1 review
Generic name: cephradine
No reviews
Generic name: cephalexin
No reviews
Ancef (Pro)
Generic name: cefazolin
No reviews
For ratings, users were asked how effective they found the medicine while considering positive/adverse effects and ease of use (1 = not effective, 10 = most effective).

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.