Q10 – Remembering antibiotics and their classes

Our JMO pre-test survey also asked “What puzzles you about antibiotics and their use”. A recurring theme was concern about remembering the various classes and names of antibiotics. Here are some useful pointers and a short quiz ! Classes of antibiotic share the same mechanisms of action (for example, antibiotics in the aminoglycosides class inhibit protein synthesis by irreversibly binding to the 30S ribosomal subunit in bacterial cells but also cause direct cell wall damage), pharmacodynamics and for the most part, toxicity potential.  Pharmacokinetics of different agents within a class may differ widely however.

Here are some tips :

As with all medications, the clue to their drug class is in their name. To begin committing them to memory, remember at least one antibiotic from each class (the easiest would be just to remember the most commonly used), remember its distinguishing naming pattern and think of other antibiotics with that same pattern. Here are some examples:

Class Pattern Example Other antibiotics in the same class
Carbapenems End with –penem Meropenem Ertapenem, Imipenem
Cephalosporins Begin with cef- Cefalexin Cefazolin, Cefoxtaxime, Ceftriaxone, Ceftazidime
Nitroimidazoles End with -nidazole Metronidazole Tinidazole
Penicillins End with -cillin Amoxycillin Ampicillin, Benzylpenicillin, Dicloxacillin
Quinolones End with -floxacin Ciprofloxacin Moxifloxacin, Norfloxacin
Rifamycins Begin with rifa- Rifaximin Rifabutin, Rifampicin
Tetracyclines End with -cycline Doxycycline Minocycline, Tetracycline

Note that by international agreement, all cephalosporins are now spelt with an ‘f’ – I know, it grates!  

Of course,  inconsistencies occur. These are part of the GLAM group – Glycopeptides, Lincosamides, Aminoglycosides and Macrolides (the GLAMorous often don’t follow convention!):

Glycopeptides

Lincosamides Aminoglycosides Macrolides
Vancomycin Clindamycin Gentamicin Clarithromycin
Teicoplanin Lincomycin Tobramycin Azithromycin
Amikacin Roxithromycin

Erythromycin

[Gentamicin is with a terminal ‘micin’, reflecting a different species of origin for this antibiotic. It may seem pedantic but don’t get this wrong – some people may assume that you are ignorant! 

The GLAM group can be harder to commit to memory but some mnemonic techniques could be useful.

  • If you want to CARE for someone, use a macrolide.
  • Give Them All aminoglycosides  (don’t!)
  • Lincosamides start with ‘lin’  (in Australia at least),  excepting linezolid (an oxazolidinone)
  • Glycopeptides- no easy way – just remember vancomycin and teicoplanin (histamine release syndrome (red man) occurs with vancomycin not teicoplanin.

Similar methods can be applied to the majority of your antifungals (-azoles and –fungins) and antivirals (-vir).   There are several other common antibiotics which don’t follow particular patterns and don’t below to specific groups (for example, trimethoprim and nitrofurantoin).

Try using the above mentioned tips in our Antibiotic Class Quiz!

If you have any tips or references for remembering antibiotics, please help by posting them in the comments section below!

References

  • Australian Medicines Handbook 2017, Australian Medicines Handbook Pty Ltd; Adelaide.

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