So you want to give your mom your (or someone else's) prescription medication that wasn't prescribed for her?
Physicians Desk Reference would be a place to start (I think) and they'll have it at the library. Their drug web site
here. For example
Vicodin, see the section on drug interactions.
But if you are worried about allergies and/or drug interactions you should probably rely on professional advice which isn't likely to come from someone qualified to give it.