Answers:
Do you want to use the herb for a condition save for hypertension?
Slippery elm may affect the digestion of conventional medicine.
Take a look at these websites from the University of Maryland Medical Center for more information:
slippery elm - http://www.umm.edu/altmed/articles/slipp...
hypertension - http://www.umm.edu/altmed/articles/hyper...
According to the info at the relation below in that is no know interactions beside other drugs and no contra indications.