- Planned use during the study of prescription medications, herbal supplements, nutritional supplements, or over-the-counter medications except as follows: multivitamins, acetaminophen (up to 650 mg every 6 hours as an analgesic), ibuprofen (up to 600 mg twice daily), naproxen (up to 500 mg twice daily for pain or headache), and Benadryl (diphenhydramine, up to 25 mg daily for insomnia or seasonal allergies) are permitted. The use of topical or locally-acting drugs (e.g., eye drops, IUDs, skin ointments) will be considered on a case-by-case basis.