Gluten is sometimes used as a filler in medications. Gluten Free Drugs is a very helpful and informative website concerning gluten and medications. The site is maintained by a pharmacist and updated often. It can be used to search for both prescription and over-the-counter (OTC) medications.
Check out Gluten Free Drugs at glutenfreedrugs.com.
Also, do not hesitate to call the 800-number on your medications. I have gotten great information by calling the manufacturers directly.