Drug Interaction Checker

Here are some resources for the check for drug interaction between medications (and some illicit drugs).

For all medicines

In a search of all free drug interaction tools, the best one we found was:

WebMD

The US government drug interaction checker we found to be difficult to use:

Rx Nav

US National Library of Medicine

For Hepatitis medicines and their interactions with medicines, street drugs and OTC drugs.

Hep Drug Interactions 

University of Liverpool