what is the rationale behind taking grapefruit with eca? grapefruit juice contains a benzofuran called bergamottin which inhibits cytochrome p450 and its isozyme which process some drugs, and make them ineffective. thats why they say not to drink grapefruit juice and certain meds, i would make sure ephedrine isnt processed by this enzyme as alot of drugs are and it could potentially make the drug less effective. however, it could make it more effective, its worth investigating for sure.