Day 3 – essential medicines

This post is a part of a series on drug shortages.

Well, day 3 has spilled over into night 3 and into day 4’s morning.

It began with the question of how to assess the impact that drug shortages have on the health care system. Now, there are a million ways to do this, but I wanted something quick and concrete, and we had discussed the idea of looking into essential medicines lists back in our 2018 paper but didn’t get around to it.

The idea is this. “Essential medicines are those that satisfy the priority health care needs of the population” according to the WHO. In service of countries maintaining availability of these important medicines, the WHO has long-maintained a Model List meant to be adopted and adapted by countries for their specific needs and the supply of these medicines protected. Canada has no such list. In a recent paper, Taglione et al., 2017 pitched a potential preliminary essential medicines list for Canada adapted from the WHO Model List through discussion with clinicians, literature reviews, and a look at prescribing patterns of family physicians. So, our thinking is that we can gauge the impact of shortages by finding the drugs involved in shortages that are also on the essential medicines list, as clearly those would be important drugs to have lost access to.

Working from the essential medicines list in the Taglione paper, and eventually from an updated list provided by the lead author, Nav Persaud, I cross-referenced shortages by ATC code. (Aside: the ATC classification system is a strict ontology that assigns short alphanumeric identifiers to each medicine based on its ingredients and organ system it acts on. An ATC code is specific to each kind of medication, but may lump together different formulations (e.g. tablet, oral liquid, IV solution) as well as the same drug made by different manufacturers. The terminology of medicines deserves it’s own post.).

The results are this: in 2019, roughly 5% of the drug shortages that occurred involved medicines on the essential medicines list. Yet, all of the medicines on the list had at least one shortage to the drugs in their ATC code group in 2019.

What to make of this? It’s not terribly surprising to me that only 5% of the shortages involved essential medicines. The published list is only about 125 items, and the updated list we received (available on is about 135. My quick analysis[1] says there are 1503 marketed medications by ATC code, so 5% is about what you’d expect all else being equal (which it absolutely isn’t, because at the very least we know that ATC codes refer to variable sized groups of drugs).

The fact that all of the medicines on the list had a shortage is concerning though. It means shortages likely are hitting us where it hurts: commonly prescribed drugs considered crucially important for a functioning health care system. Of course, simply because one drug goes into shortage does not mean that it cannot be substituted with an alternative dosing format (e.g. if 325mg Tylenol tablets go into shortage we can substitute them with 500mg Tylenol tablets, for instance), or with a different manufacturer’s drug of the same kind (e.g. a generic brand Acetaminophen tablet), or even substituting with a different medication in the same class (e.g. using a different NSAID if Ibuprofen is in short supply).

I’m sure I’ll have more to say on the matter in future posts. In the meantime, if you’d like to see details on this and other analyses I’ve been doing, please visit:

I will be updating that site as I go along.

[1] Here’s the R code I used with tables from the Drug Product Database extracts:

dpd_status %>% 
	inner_join(dpd_ther) %>% 
	group_by(TC_ATC_NUMBER) %>% summarize() %>% count()Code language: R (r)