Monday, December 27, 2010

Why are the letters "z" and "x" so popular in drug names?

Freelance medical and science writer Rob Stepney noticed the rapid growth of "x" and "z"-named products included in the British National Formulary (BNF). So for the Christmas 2010 issue of BMJ (Stepney, 2010), he investigated this phenomenon:
Of 1436 products added to the BNF between 1986 and 2005, more than a fifth had names that began with z or x or contained a prominent x or z within them. In 1986, only 19 branded drugs began with one of these letters. Over the next two decades, the number of brands beginning with a z increased by more than 400% (to 63) and those beginning with an x increased by 130% (to 16). In the same period, the overall content of the BNF grew by only 80%.
Why did it happen? He first asks whether use of the voiced fricative “zuh” sound might be special in some way, but he quickly dismisses this possibility, along with the popularity of z in the Middle East.

Instead, he speculates that x and z might have been perceived as making products stand out in a crowd:
Reflecting their infrequent occurrence in English words, x and z count for 8 and 10 points in Scrabble, the highest values (along with j and q) in the game. So names that contain them are likely to seem special and be memorable. “If you meet them in running text, they stand out,” is the way one industry insider explained. Generally, they are also easy to pronounce.
In my view, however, the rush to uniqueness resulted in an overcrowded field. The market became saturated with X and Z brand names, which can cause confusion.

Fig 1 (Stepney, 2010). Number of drugs with a brand name beginning with z or x listed in March edition of BNF for each year. New formulations of existing brands and zinc related compounds have been excluded.

For instance, the August 9, 2007 newsletter from the Institute for Safe Medication Practices discusses Progress with preventing name confusion errors and links to a document on the most problematic look-alike and sound-alike drug names of 2006-2007 (PDF). These include:
ZYPREXA (olanzapine) and ZYRTEC (cetirizine)

Name similarity has resulted in frequent mixups between Zyrtec, an antihistamine, and Zyprexa, an antipsychotic. Patients who receive Zyprexa in error have reported dizziness, sometimes leading to a related injury from a fall. Patients on Zyprexa for a mental illness have relapsed when given Zyrtec in error.
Other frequently confused Z/X pairs:
Zantac – Xanax
Zantac – Zyrtec
Zestril – Zyprexa
Zestril – Zetia
Zocor – Zyrtec
At any rate, here's Stepney's (2010) conclusion:
I suggest that this phenomenon arose because of the fast rate at which new products were being introduced, the fact that the difference between many “me too” drugs was more apparent than real, the immense rewards that were seen to accrue from innovative marketing, and the fact that the ploys available for use in the naming of drugs are so restricted.
A full list of the drugs mentioned in the article can be viewed here.


Stepney, R. (2010). A dose by any other name would not sell as sweet. BMJ, 341:c6895 DOI: 10.1136/bmj.c6895

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At December 28, 2010 2:06 AM, Blogger Neuroskeptic said...

Z and X are just "cool" letters. If you're selling a drug, you want it to have a cool name. "A rose by any other name would smell as sweet" but a Zyprexa by any other name might not sell quite as well... of course it might also get confused with stuff and lead to horrible mistakes but that's not the marketing department's problem!

At December 28, 2010 3:38 AM, Blogger gregory said...

next topic, the names of new companies in the internet age ... all so weird, but probably the only domain names that were available.

At December 28, 2010 1:42 PM, Anonymous Sheffield Colocation said...

It's easier to make up words starting with those letters without referring to any verbs. Words starting with those letters are used less commonly or in niche context, people want a drug which is specialised to their ailment.

I know what I'll be doing next time I'm waiting at the chemist though, looking at brands names.

At December 28, 2010 1:54 PM, Anonymous Anonymous said...

for more on this topic check out this url:

this guy shows/quantifies that X and Z are insanely over-represented in drug names when comparing with normal written english.

At December 28, 2010 4:09 PM, Blogger Barry Kelly said...

The numbers in this article are very frustrating, and the graph is misleading. The rise in absolute popularity of drugs with names with z and x has a lot less meaning if it's not presented along with the rise in total drugs too. That number (80% rise) is also mentioned, but you have to do mental arithmetic to figure out how that affects the other numbers, and it doesn't help you normalize the graph.

In fact, judging by the graph, if the total number of drugs increased by 80%, it looks like the relative popularity of "x" is actually static / declining over time.

All numbers for increases in popularity of x and z should have been normalized to the increase in drug count; in other words, described as an increase in the share of the total set of drug names (or share of new market entrants, or whatever).

At December 28, 2010 7:11 PM, Blogger The Neurocritic said...

Thanks for the comments.

Neuroskeptic - Stepney did note the following about cool car names: "Of the 10 cars currently listed as fastest in the world (all capable of 0-60 mph in under four seconds), four—including the Ferrari Enzo and the Jaguar XJ220—have a z or x in their names."

The "cool" letters aren't entirely gender-specific, either. Zelnorm (tegaserod) was a drug for IBS marketed specifically to women (before it was removed from the market in 2007).

This raises the question, Who is the target of branding? The patient? The prescribing doctor? Direct-to-consumer advertising on TV wasn't allowed in the U.S. until 1997, and it's not allowed in most other countries. Z-names started their rise before then, so it would seem that doctors are the target.

Anonymous - Thanks for providing that link. Here's part of a blog entry at Pharmaceutical Journal Online, written by "Bystander"

The X to Z of proprietary names
27 Mar 2010

...Nowadays companies pay vast sums to branding specialists, and the current trend among these self-appointed experts is to suggest short zappy names. These names frequently contain the consonants X or Z or both.

Why? Apparently these letters tend to be associated with high technology and innovation and are thought to convey a subliminal indication of power. They are also deemed to have a strong impact in print. Other favoured consonants include D and a hard C, while the most popular vowels are A, O and Y.

All these elements harden the sound of the product name. According to one branding expert: “The harder the tonality of the name, the more efficacious the product in the mind of the physician and the end user.”

I also found an interesting 1996 article in BMJ: Product names, proper claims? More ethical issues in the marketing of drugs.

Barry Kelly - The Book of Odds post does a nice job of comparing the frequencies of letters in the English language vs. letters in drug names. But yes, a normalized graph would have been nice.

At December 28, 2010 7:53 PM, Blogger Anthony said...

If you've got a Lexis/Nexis subscription, The New Republic had a short piece on "the iron law of scrabble" (or something like that), which said that your technical product sounds more techy the higher its scrabble score, or perhaps its average scrabble score per letter. The examples used were popular cars of the time, including the 280Z, and explaining that Chrysler's K-Cars didn't even *sound* cool.

At December 28, 2010 10:46 PM, Blogger DNAutics said...

Part of it is that since the development of combinatorial chemistry and medicinal chemistry a lot of the chemical groups that are starting to appear are oXaZoles, and thiaZoles, triaZoles, etc. The letters X and Z are overrepresented in the chemical lexicon as well.

At December 30, 2010 1:17 PM, Anonymous Anonymous said...

I think it's because the letters z and x sound kind of space age, and seem more scientific. Also, a lot of chemical names use z's in the suffixes, like "-azine" and "azide" which might lead to the brand name trying to include part of the generic name, to assist with remembering the name of the medication.

True story, only tangentially related to this, but which underscores the meaning of medication names: a patient years ago refused to take Stelazine (trifluperazine) because he thought it meant we were trying to turn him into a woman (say the name out loud and you'll see) but allowed Haldol (haloperidol) or Thorazine (chlorpromazine) becuase they had "masculine" names.

At January 03, 2011 11:38 AM, Anonymous Anonymous said...

Yes, remember what happened to "Nasalcrom"? I remember the commercial started, "Nasalcrom. Yes, you heard it right." It might have lasted a little longer if they called it Zaselcrom!

At January 05, 2011 1:27 PM, Blogger kami said...

Voto por el primer comentario :)
Z y X son cool, en consecuencia, deben ir con las drogas.
Es como las propagandas de cigarrillos en el siglo pasado...

At March 19, 2013 1:14 PM, Anonymous John Pritchett said...

It appears to me that more drug names end with the letter "a" than any other letter. See:

At May 20, 2016 11:56 AM, Blogger DianaGMeyers said...

@chemdroid.. very interesting to me.
I had a dream that I shouldn't take any drugs with an x in them. That is what led me to this page. You are suggesting that its possible different chemicals work on different people differently and perhaps my dream was valid with advice.

At March 16, 2018 7:03 AM, Blogger Unknown said...

I HATE these new names! I can't remember any of them! Ridiculous!

At March 13, 2024 3:18 AM, Blogger Education said...

words that start with x


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