i read a little bit about it and this is what i found out.

It has been made a prescription-only drug in the Irish Republic because of anxieties about its possible similarity to MAOI antidepressants.)

St Johnâ??s Wort may prolong the effects of some sleeping pills and anaesthetics.

this guy toook coedine, weed tea and st johns wort
http://www.erowid.org/experiences/exp.php?ID=9358

There is not really very much about mixing it with other drugs and as i have no personal experiance with it this is all the infomation i can give you.....HOWEVER it has made me interested in trying st johns wort so i might just do that. thanks