<<Disclaimer: Verify this information before applying it to your situation.>>

I went to the website of Robitussin's maker (Whitehall Robbins
Healthcare Products)  to see if their product was the source of the DH
and gut distress that affected me last night. (It was one of several
suspects.)  There was a link to a FAQ for Robitussin.  Below are the
total contents of that FAQ page

> Thank you for visiting the Robitussin FAQ. We will be adding more questions
> and answers in the future.
>
>   1. Does Robitussin contain gluten?
>
>    No. Robitussin is gluten free.

(Oh well, maybe my wife was a little careless about the meat loaf she
made.)