Antibiotic classes – why so important to know about them?

The antibiotic knowledge survey of our new interns this week,  showed that many were confused about which class vancomycin (a glycopeptide) fell into (30% thought it was an aminoglycoside).  This is a potentially dangerous confusion as the dosing, side effects and monitoring all differ substantially between these classes:

Aminoglycoside Glycopeptide
Indicative agents Gentamicin Vancomycin
Dosing By ideal body weight (IBW) if actual weight > 20% over IBW Actual weight ( see below)
Loading dose No (higher dose in severe sepsis) Yes
Monitoring Not required for short course (3 daily dose) therapy Yes (just prior to 4th dose)
Toxicity Renal (cumulative)

Ototoxicity (idiosyncratic and cumulative)

Renal (associated with sustained levels above 25mg/L)

Ototoxicity possible but rare

AIMED postings of relevance Safe use of aminoglycosides Dosing of vancomycin in obese patients

The schema below worthy of further study!  Particularly focus on betalactams, aminoglycosides, glycopeptides, sulphonamides, tetracyclines and quinolones to start with.  This antimicrobial agent study proforma is a useful way to start documenting your knowledge.

An important aspect of antibiotic allergy surrounds the betalactam class – see these postings for useful allergy explanations from our experts.

Reference

The current Therapeutic Guidelines: Antibiotic is a useful starting point – look to the introductory chapter and the appendices on aminoglycosides and vancomycin. However, as a prescriber, you will need to know more than that !

5 comments

  1. Hi,
    Thanks for the post!
    Could you please provide the reference for the schema? Can’t quite read it!
    Thanks so much

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  2. AMG dosing weight is incorrect. Use Adjusted body weight if actual weight is > 120% of ideal body wt.

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  3. […] are shared within a class- dose routine, toxicity, type of action and resistance . For more, see this posting on our antibiotic stewardship […]

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  4. […] the cell wall – revise mechanisms of action for the major classes of antibiotics (see the posting 1  and posting 2 from […]

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