For more than half a century, we have classified psychiatric drugs by their main indication. So we have used the terms antidepressants, antipsychotics, anxiolytics, hypnotics, mood stabilizers and so on. But this system has several disadvantages.
First, it does not reflect the fact that our prescribing in reality is pragmatic, and not confined by “indication”. We may use drugs labeled as antidepressants in certain patients with anxiety disorders, or a second generation antipsychotic in someone with depression but no evidence of psychosis. This can cause confusion and distress in patients which, in turn, may contribute to poor adherence.
Since it is based on neuroscience, the new system embeds our understanding of how drugs work
Secondly, the traditional classification does not help clinicians make informed choices about the next steps to take in therapy – if additional treatment is needed -- based on the likely benefit and possible side effects of different agents.
And, thirdly, the core classification based on indications has trouble keeping up with changes in diagnostic categories.
In all three respects, classifying drugs not by indication but by pharmacology and mechanism of action would help. And a mechanism-based classification is exactly what underlies the newly-developed Neuroscience-based Nomenclature (NbN).
In centering the new system on mechanism of action we are following what is done, for example, in hypertension – where we have diuretics, beta blockers, calcium antagonists, ACE inhibitors and angiotensin II antagonists. This encourages our colleagues in cardiovascular medicine to augment efficacy by adding a medication with a different mechanism. It also helps avoid additive toxicities.
When it comes to psychotropic medication, we also need a system that helps answer the question: what does pharmacology suggest should be the next step? It is hoped that the new nomenclature will be a tool to help clinicians make informed decisions.
Our understanding contributes to the way we classify drugs, and the way we classify drugs contributes to our understanding of how best to use them
In addition to being consistent with patterns of prescribing – and encouraging the rational use of drugs -- we can reasonably expect a classification system to be based on our current understanding of neuroscience. It should also be “future proof”, in the sense that it can accommodate new classes of compound that target novel pharmacological domains or have as yet undiscovered mechanisms of action. The NbN meets these expectations.