Is it safe to take 5htp with vyvanse (lisdexamfetamine)?

Not yet: There is no reported drug drug interaction, however the national institutes of health recommends not to use 5-htp until more is known. 5-htp might be unsafe. Some people who have taken it have come down with eosinophilia-myalgia syndrome (ems), a serious condition involving extreme muscle tenderness (myalgia) and blood abnormalities (eosinophilia).

Vyvanse/5HT: No adverse interactions.