I called one drug company and their reply was "If there's any gluten in it, it would only be a small amount." Didn't build my confidence. And then I had the experience of being told one product was gluten free, but after three days of misery on it, I concluded it was contaminated by the packaging process.
I probably run this theme by too often, but again I like
www.napervillegi.com. It's a support group in Naperville, Ill, which has taken it upon themselves to continually call both food and drug manufacturers to determine which products are gluten free. Then they publish their extensive lists free of charge on the website. They don't guarantee it's perfect, as things can change, but I figure their legwork in this area is just as sound as mine would be, so I trust them. And they update every few weeks or so.
Just go to the website and follow the links.