Hi Annasnow there is an app you can get for both I phones and android devices called Hep I chart.
Its from the University of Liverpool and it has a comprehensive list of drugs. Its really easy to use as well. My hep nurse back here in NZ swears by it.
Also if you type into the search bar of the forum "Drug Interactions" it will bring up all the posts.
The GP cheat sheet contains links to pretty much everything needed including the interactions checker. You can get to it from the forum tabs, the forum menu, as well as other links. If you just add /gp to the domain name