Towards a focus on the science in treatment classifications

Confusions in old drug classifications

Until recently, the naming of drugs in psychiatry was based on the core disease symptoms (antidepressants, antipsychotics, etc.). These classifications of drugs gave no information on their mode of action, so could not help physicians make rational treatment plans, particularly for second-line treatment options or adjunctive therapies.

Old drug nomenclature could cause patient confusion and stigmatization

A future-proofed nomenclature

The Nomenclature Taskforce was set up in 2008, with representatives from ECNP, ACNP, AsCNP, CINP and IUPHAR. The aim of the taskforce was to improve the drug nomenclature in psychopharmacology. In particular, they sought to develop a nomenclature based on current neuroscientific knowledge, that would be ‘future proof’; that is, capable of accommodating new compounds with new mechanisms of action. It was hoped that such a new nomenclature would help clinicians make informed choices about patients’ medications, and decrease stigma and improve adherence by providing patients with a rationale for their choice of treatment.

The nomenclature developed was named Neuroscience-based-Nomenclature,¹ now in its updated form it is known as (NbN-2).² This most recent version now incorporates 134 medications, with new drugs added at each update. The classification is based on current knowledge of the drug’s pharmacology using 10 pharmacological domains: Acetylcholine, Dopamine, GABA, Glutamate, Histamine, Melatonin, Norepinephrine, Opioid, Orexin, Serotonin. These are combined with different modes of action: Enzyme inhibitor, Enzyme modulator, Ion-channel blocker, Neurotransmitter releaser, Positive allosteric modulator (PAM), Receptor agonist, Receptor antagonist, Receptor partial agonist, Reuptake inhibitor. There are four other dimensions: Approved indications (from major regulatory bodies), Efficacy and Side Effects (from reliable clinical data), Practical Note (a summary of clinical knowledge), and Neurobiology (both preclinical and clinical). This information has been presented in the NbN book, and more importantly in a freely available app that makes this nomenclature widely accessible.

NbN is based on current knowledge of a drug’s pharmacology and mode of action

Changing our vocabulary

One effect of this nomenclature change is to expand our vocabulary – the NbN classification contains 60 groups of drugs with different pharmacologies and modes of action, rather than a few disease indications. On the other hand, the NbN may make obsolete terms such as antidepressant and antipsychotic – as we get used to speaking instead about ‘drugs with an antidepressant effect’ or ‘drugs with antipsychotic actions’.

We may have to change the way we speak about drugs

Highlighting gaps in our knowledge

Another interesting effect of this nomenclature is that it highlights the fact that many drugs with different pharmacologies and modes of action may be used to treat a single indication (so clearly there is no one mechanism of drug action that is effective in, say, depression). In addition, some drugs are used at different doses to treat different indications. It is now known that some of these drugs have different pharmacologies and modes of action at those different doses, but it is unclear whether those different modes of action account for the drugs efficacy in particular indications. For example, some drugs originally developed to treat psychosis and now being used to treat other disorders have effects at different receptors depending on the dose used. This presents a challenge for the NbN: such drugs arguably should have different nomenclatures, depending on the indication they are being used in, and therefore their dose.

The NbN is an evolving classification, based on current knowledge and incorporating new findings and new drugs at each regular update. The NbN taskforce is also actively seeking feedback on the nomenclature and on the App, to keep improving this process.