I heard today from a doctor that the MOA for most drugs is actually 'unknown'! Wow, can this be true? I skimmed thru a pharmacology book, it looked pretty convincing but ultimately but didn't state any percentages.

So, my question is how much (%) of commercially available medical drugs have a known MOA? And I mean really known to the deepest level, without any doubt.

Thanks, pom


1 Answer 1


Mechanism of Action (MOA) refers to the effects of a drug on a molecular level (receptors, chemical reactions) and Mode of Action (MoA) to the effects on a functional or tissue level, which are more observable. So, actually, in most cases, we know how a drug works, because we can see its effects, but we may not know "how exactly" it works.

Wikipedia has a short list (far from complete) of 67 drugs with unknown mechanisms of action.

On DrugBank, you can see that mechanism of action for many drugs, including some very well known, such as ibuprofen, is "not known" or "not completely understood," etc. Despite that, the main effects of the approved drugs are known otherwise there would be no good reason to use them.

Even if the data about "mechanism of action" or "pharmacological action" are presented in detail on sites, like DrugBank, Drugs.com, DailyMed and RxList, you can't really search them in the way to find a "percent" of drugs with known or unknown mechanisms.

  • ok, thanks Jan, good answer. I'll wait a few days and then accept this as correct.
    – Pompair
    Oct 21, 2019 at 16:02
  • I'd add that especially for psychoactive substances we often know the (sometimes numerous) molecular targets, but not which one or where in the brain the effect occurs that is associated with the outcome of interest.
    – Bryan Krause
    Oct 24, 2019 at 1:26

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