First-Generation Cephalosporins – What are they?

Cephalosporin generations have confused tens of thousands of students; their names and individual characteristics proving to be nothing other than a nexus of confusion. Here, we go some way toward clarifying what is otherwise an arcane subject.

Whilst we are examining second generation cephalosporins here, you can find the other generations in the links below:

Each review goes through the main examples of each class, their pharmacology, what differentiates them from earlier and later classes, as well as assessing some of the main side effects and drug interactions associated with each generation.

What are 1st Generation Cephalosporins?

First generation cephalosporins are, like their successor generations, members of the β-lactam class of antibacterial drugs.

Like other beta-lactams, cephalosporins are bactericidal in effect – meaning that they actively kill bacteria rather than merely suppressing their growth (an effect that defines bacteriostatic antibacterials).

First generation cephalosporins include drugs such as:

  • Cefadroxil
  • Cefalexin
  • Cefazolin
  • Cefradine (not available in US)

First generation cephalosporins are simple to remember. Unlike members of subsequent generations, first-generation drugs contain ‘cefa’ at the beginning of their names. A quick and easy mnemonic would be: ‘The Ex of an Ox in the Zoo – Cefalexin, Cefadroxil, Cefazolin’.

First-Generation Cephalosporins

There are an unlimited number of mnemonic variations one could try. Here’s another quick example: ‘The Fox Exits the Zoo – Cefadroxil, Cefalexin, Cefazolin’. Knowing that first-generation drugs always have ‘cefa’ at the start, we can be as imaginative as we like.

Spectrum of Activity

First generation cephalosporins have broad-spectrum of activity. Let’s review some of their main pharmacological features:

  • In terms of cephalosporin generations, they have the least activity against Gram-negative organisms. By the same token, though, they also have the most activity against Gram-positive organisms.
  • In terms of Gram-positive powers, they have activity against staphylococci and most streptococci.
  • However, they have no activity against MRSA or enterococci.
  • In terms of their Gram-negative activity, first-generation drugs are active against PEcK: Proteus mirabilis, Escherichia coli, and Klebsiella pneumoniae.
  • As the earliest generation, they’re more susceptible to β-lactamase mediated hydrolysis of the β-lactam ring when compared to later generations.
  • They are generally well-absorbed from the gut. Cefazolin given parenterally.

Unwanted effects with this class are similar with other generations.

Side effects include diarrhea, nausea and vomiting. Some patients also experience dizziness, headache and abdominal pain. The propensity of each effect depends on the drug in question.

Check out the links at the top of this page for more information on the pharmacology of the remaining cephalosporin generations.

By | 2016-12-14T10:20:37+00:00 December 13th, 2016|Pharmacology Guides|0 Comments

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