This chapter is related to the aims of Section F11(i) from the 2017 CICM Primary Syllabus, which expects the exam-going trainees to be able to "describe the pharmacology of anti-asthma drugs". Unfortunately, though the examiners seem to love asthma, their love is expressed in the form of vague and haphazard gestures. Often, the questions will refer loosely to "drug groups commonly used to treat acute severe asthma", without specific boundaries, as if to test the candidates' capacity for self-control. Come on, we dare you: describe all the mechanisms. This sort of stem is highly unhelpful, as asthma is a complex disease and drugs which are used to treat it come from a whole variety of classes. Taken completely literally, this syllabus item would also cover steroids, magnesium sulphate, ketamine, helium-oxygen mixtures and the halogenated anaesthetic ethers.
Of course, a normal person would conclude that this would be insane, and that surely the college examiners expect a narrow focus; i.e. the question really asks "discuss the pharmacodynamics of bronchodilators". But in fact that is not the case. From the fragmented debris of past papers, one is able to reconstruct the incomplete skeletons of marking criteria, and this reveals that the examiners expected everything:
Desirable elements in the answers included:
We also know they did not want:
Anyway. Given the vagueness and breadth of the SAQ, it is remarkable that in most cases the trainees do very well in answering it. Historically, the pass rates are in the order of 70%. Past paper questions which involved this subject were:
In the interest of preserving some attachment to reality (i.e. what can be reasonably expected from a ten minute answer) the table offered here produces a minimalist entry for each class of drug, as well as a couple of examples, rather than a full-scale pharmacological breakdown (absorption, distribution., elimination, etcetera). Where possible, a faint trail of references is left for the trainee to follow, in case they need more details from peer-reviewed publications.
Mechanism of action | Examples |
β-agonists (Waldeck, 2002) | |
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Antimuscarinic agents (Soler & Ramsdell, 2014) | |
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Corticosteroids (PJ Barnes, 1996) | |
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Methylxanthines (Tilley, 2011) | |
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Magnesium sulphate (Noppen, 1990; Irazuzta et al, 2017) | |
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Ketamine (Goyal & Agrawal, 2013; Sato et al, 1998) | |
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Volatile anaesthetics (Mondoñedo et al, 2015; Yamakage, 2002) | |
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Helium-oxygen mixtures | |
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Zdanowicz, Martin M. "Pharmacotherapy of asthma." American journal of pharmaceutical education 71.5 (2007).
Waldeck, Bertil. "β-Adrenoceptor agonists and asthma—100 years of development." European journal of pharmacology 445.1-2 (2002): 1-12.
Soler, Xavier, and Joe Ramsdell. "Anticholinergics/antimuscarinic drugs in asthma." Current allergy and asthma reports 14.12 (2014): 484.
Barnes, Peter J. "Molecular mechanisms of steroid action in asthma." Journal of allergy and clinical immunology 97.1 (1996): 159-168.
Tilley, Stephen L. "Methylxanthines in asthma." Methylxanthines. Springer, Berlin, Heidelberg, 2011. 439-456.
Noppen, Marc, et al. "Bronchodilating effect of intravenous magnesium sulfate in acute severe bronchial asthma." Chest 97.2 (1990): 373-376.
Irazuzta, Jose Enrique, and Nicolas Chiriboga. "Magnesium sulfate infusion for acute asthma in the emergency department." Jornal de pediatria 93 (2017): 19-25.
Goyal, Shweta, and Amit Agrawal. "Ketamine in status asthmaticus: a review." Indian journal of critical care medicine: peer-reviewed, official publication of Indian Society of Critical Care Medicine 17.3 (2013): 154.
Sato, Tetsumi, et al. "The role of the N-methyl-D-aspartic acid receptor in the relaxant effect of ketamine on tracheal smooth muscle." Anesthesia & Analgesia 87.6 (1998): 1383-1388.
Khan, Khurram Saleem, Ivan Hayes, and Donal J. Buggy. "Pharmacology of anaesthetic agents II: inhalation anaesthetic agents." Continuing Education in Anaesthesia, Critical Care & Pain 14.3 (2014): 106-111.
Mondoñedo, Jarred R., et al. "Volatile anesthetics and the treatment of severe bronchospasm: a concept of targeted delivery." Drug Discovery Today: Disease Models 15 (2015): 43-50.
Yamakage, M. "Editorial II: Effects of anaesthetic agents on airway smooth muscles." (2002): 624-627.