1st and 2nd generation antibiotics

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I find it hard to understand 1st, 2nd generation and so forth and so on of antibiotics! Please ! Desperately need the help of everyone!

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Specializes in med/surg, telemetry, IV therapy, mgmt.

The only drugs I can think of that are referred to in terms of "generations" are the pencillins and cephalosporins. It was actually hard to find Internet references until I got my search words correct (generation classification system of penicillin)

This article on the Wikipedia website about Cephalosporins (Cephalosporin - Wikipedia) refers to the "generation" classification system itself and has this to say "Cephalosporins are sometimes grouped into "generations" by their antimicrobial properties. The first cephalosporins were designated first generation while later, more extended spectrum cephalosporins were classified as second generation cephalosporins. Each newer generation of cephalosporins has significantly greater Gram-negative antimicrobial properties than the preceding generation, in most cases with decreased activity against Gram-positive organisms. Fourth generation cephalosporins, however, have true broad spectrum activity." and "The classification of cephalosporins into "generations" is commonly practised. . ." Here are two other articles that discusses the "generation" classification of cephalosporins: Answers - The Most Trusted Place for Answering Life's Questions

Here is a link to a pharmacology school webpage on antibacterial drugs. About 1/4 of the way down the page is a box the lists the four generations of cephalosporins and what drugs are in each group and what they are used to treat. If you keep on reading down it discusses the use of the drugs in each of the four categories and gives more information about the categories. There is also some information there about beta-lactamases and resistance to penicillin.

This is what my pharmacology textbook says about penicillins. It includes the cephalosporins with the penicillins (I'm paraphrasing):

First-Generation

  • penicillin G and penicillin V
  • have a narrow spectrum of clinical use (this means there are only a few organisms that they are able to successfully treat with this class of penicillin)
  • good for common gram-positive bacteria that cause ear and throat infections, venereal diseases of gonorrhea and syphilis, and staph infections due to Staphylococcus aureus that cause abscesses, endocarditis and pneumonia
  • a very high number of the drugs in this group are resistant to organisms that produce penicillinase [Penicillinase is an enzyme that some bacteria are capable of producing. This enzyme is also called a beta-lactamase and it inactivates some of the penicillins.]

Second-Generation

  • ampicillin, amoxicillin
  • have an extended or broad spectrum of clinical use
  • work equally as well as penicillin G class plus effective against Escherichia coli, Proteus mirabilis and Haemophilus influenzae which are associated with urinary, respiratory and ear infections
  • all drugs in this class can be taken orally as they are well-absorbed from the GI tract. Patients will get higher plasma levels of amoxicillin than with ampicillin, so amoxicillin is more frequently ordered
  • ampicillin can also be given IM or IV
  • not very effective against penicillinase-producing organisms

Third-Generation

  • carbenicillin and ticarcillin
  • carbenicillin can be given orally; ticarcillin is given IM or IV
  • broader spectrum of use than the second-generation penicillins
  • used in the treatment of serious urinary, respiratory and bacteremic infections due to gram-negative Pseudomonas aeruginosa and Proteus vulgaris
  • not resistant to penicillinase-producing organisms

Fourth-Generation

  • mezlocillin sodium, piperacillin
  • more potent than the other three classes
  • given IM or IV
  • have less sodium salt in them than the other penicillins so if a patient has congestive heart failure and needs restricted sodium intake this may be a reason for the doctor choosing one of these penicillins for them
  • used for serious infections due to Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae and Bacteroides fragilis in combination with other antibiotics
  • not resistant to penicillinase-producing organisms
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Thank guys!!!!!!!!!!!!

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Here is classification of cephalosporins generations:

http://www.emedexpert.com/classes/antibiotics.shtml

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