Canada's Adverse Drug Reactions Database - a database of suspected adverse reactions to marketed therapeutic products reported to the program directly by health care professionals, consumers or through the pharmaceutical manufacturer
Flockhart's P450-based Drug Interaction Tables
Metabolism and Transport Drug Interaction Database (subscription) - contains in vitro and in vivo information on drug interactions in humans from 5765 publications referenced in Medline and from 205 product labels.
TP-Search - database of drug transporters from multiple species that influence drug distribution and elimination