List the different mechanisms of drug actions with examples
A good answer to this question required candidates to think broadly about how drugs act
and have a system for classifying their actions. One possible classification is action via
receptors or non-receptor actions. Many candidates used categories such as
physiochemical, receptor and enzymes. Common problems were failure to mention a whole
class of drug actions e.g. drugs acting via voltage-gated ion channels or gene transcription
regulation. Candidates also gave far too much detail in some sections e.g. a description of
zero order and first order kinetics is not required. Candidates often did not give examples of
the drug action they described.
This is actually a very difficult question to answer, as there are no formal or widely accepted systems for classifying mechanisms of drug action. Attempts to make a system into something simple and general leads to reductive madness like Bjornsson's therapeutic categories (eg. "preventative", "directed at specific aetiology", etc) or to a hyperproliferation of malignant code categories (like the WHO's monstrous five-tiered ATC classification). Neither is a particularly attractive option for the exam candidate who just wants to produce an answer which suggests that they "think broadly about how drugs act and have a system".
The following suggested system was generated using an article by Imming et al (2004), who were forced to generate a classification in order to compile a pharmacology teaching curriculum. Their system (TCAT) focused on drug targets as the top-level tier. The author of Φ then took creative liberties to explore these targets and list the mechanisms via which drugs interact with them in some sort of systematic order. The exam candidate should not develop the impression that this system is an acceptable answer for this SAQ (though in all honesty it is impossible to guess what an acceptable answer might have been from the official CICM commentary).
Non-receptor mechanisms of drug action:
Receptor mechanisms of drug action:
Types of molecular receptor targets and signalling pathways
Mahoney, A., and J. Evans. "Comparing drug classification systems." AMIA... Annual Symposium proceedings. AMIA Symposium. 2008.
Imming, P., et al. "A classification of drug substances according to their mechanism of action." Die Pharmazie-An International Journal of Pharmaceutical Sciences 59.8 (2004): 579-589.
Bjornsson, Thorir D. "A classification of drug action based on therapeutic effects." The Journal of Clinical Pharmacology36.8 (1996): 669-673.
Swinney, David C. "Biochemical mechanisms of drug action: what does it take for success?." Nature reviews Drug discovery 3.9 (2004): 801-808.
Goldstein, Avram, Lewis Aronow, and Sumner M. Kalman. "Principles of drug action; the basis of pharmacology." Wiley, 1968