Differences Between Generations of Cephalosporins

Cephalosporin drugs fight a broad range of bacteria.
Cephalosporin drugs fight a broad range of bacteria. (Image: Influx Productions/Photodisc/Getty Images)

Cephalosporins are a group of antibiotics related to penicillin in structure and the way they fight infection. They are considered “broad-range” antibiotics and cover a wider range of infections than penicillin. Cephalosporins were discovered in fungus in 1949. Most cephalsporins act as bactericides. There are currently four generations of cephalosporins recognized in the United States.

First Generation

First generation cephalosporins are effective in fighting gram-positive bacteria such as strains of staphylococcus and streptococcus. Among first generation cephalosporin antibiotics are Ancef and Kefzol (cefazolin) and Keflex (cephalexin).

Second Generation

In addition to the gram-positive effects of the first generation drugs, second generation cephalosporins expand coverage to gram-negative bacteria such as enterobacter, pseudomonas and salmonella. Second generation drugs vary in coverage, and testing is often required to determine the appropriate agent to prescribe. Among second generation drugs are Cefzil (cefprozil), Ceclor (cefaclor) and Lorabid (loracarbef). The only second generation cephalosporin that crosses the blood brain barrier is cefuroxime; therefore, it is used to treat meningitis.

Third Generation

Third generation cephalosporins extend coverage of gram-negative organisms. These drugs have the ability to penetrate the central nervous system to treat infections that affect the neurological system. These third generation drugs also require testing for determination of the appropriate agent. Among third generation cephalosporins are Omnicef (cefdinir), Rocephin (ceftriaxone) and Suprax (cefixime).

Fourth Generation

As of 2010, a fourth generation of cephalosporins is in development that will be used to treat Methicillin-resistant Staphylococcus aureus (MRSA).


Cephalosporins should not be used with the following medications: calcium acetate, calcium, chloride, calcium gluceptate, calcium cluconate, Lactated Ringer's solution or Ringer's solution. If a cephalosporin drug must be used with one of these medications, your health care provider may alter the doses. Cephalosporins should not be used with Heparin. Drinking alcohol is not recommended when using a cephalosporin drug.

Medical Conditions

Some cephalosporins interact with the following medical conditions: bleeding problems, kidney disease, liver disease or gastrointestinal conditions. Inform your health care provider if you carry any of these diagnoses.

Additional Information

The cephalosporin class of antibiotic does not effectively penetrate prostatic tissue. The drug crosses fetal barriers and is also found in breast milk. Some cephalosporins have been shown to be effective in children, and carry no additional side effects to those experienced by adults. Not all the drugs have been tested in children. The drug class has not been shown to cause birth defects. While the agents do appear in breast milk, they have not been shown to cause any adverse effects to nursing infants.

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