I had to delete my other post. This is what I was looking for...
Grapefruit seed extract is not associated with any side effects, drug interactions, or contraindications. However, a number of medications should not be taken with grapefruit juice itself. These include certain immunosuppressants, cholesterol-lowering drugs, and antihistamines - if in doubt consult a physician. Furthermore, when taken as recommended it does not destroy the ‘healthy’ bacteria that reside in the gastro-intestinal tract.
Here is the link: http://www.ambertech.com/herbs/grapefruit_seed.php