Xanax and verbs

I read Nevada Barr's latest novel, Burn, over the weekend and was pulled up by this sentence:

Her Xanax were upstairs in the medicine cabinet.

They were? I mean, it was?

Yeah. For me, Xanax, like other drugs that come in pills, is nevertheless a mass noun.

• Her Xanax was upstairs
• Her Tylenol was upstairs
• Her Advil was upstairs
• Her Zoloft was upstairs

even

• Her aspirin was upstairs

You get the picture.

If I had to make it plural, I wouldn't use Xanax, like it was deer or fish or something. I'd use Xanaxes. Googling quickly, I see I'm not alone.

• How can I get hold of valium, if xanaxes r bleak 4 u?
• I always do stupid stuff when I get on Xanaxes.
• Can you take xanaxes with suboxones?
• If you swallow xanaxes, will it show up in a hair follicle?
• my search resulted only in finding out about xanaxes, which together with tramadols seemed like a very nice combination

That last one also pluralizes Tramadol, and in fact lots of people pluralize all the drug names (Vicodins, Zolofts, Valiums, Advils)... Clearly, for many people the fact that these things come in individual pills make them plain old count nouns.

But "Xanax" as the plural is is out there, too. True, most of the Google hits on "Xanax were" were false positives (like "deaths attributable to Xanax were", "patients on Xanax were", "How much Xanax were you really taking", "Last year 37.5 million prescriptions of Xanax were written", or "Halcion and Xanax were", or even "it would be great if Xanax were not addictive" ) but a few weren't. I found

• These green xanax were given to them so they would rest better at night
• I thought I was the only one who remembered that 1mg Xanax were originally purple in the US.
• aint tried vals but xanax were very nice/ wicked packaging
• the pharmacy wouldn't let me fill it, because the xanax were already in the computers

It looks as though we can safely say that medical and pharmaceutical professionals use Xanax as a mass noun, and so do most other people. A few use it as a count noun, and about half of them have the irregular plural "Xanax" while the others have a regular "Xanaxes".