When on medications, you’ve been told not to drink grapefruit juice. Why?
The citrus fruit inhibits intestinal enzymes that metabolize many medications. In order to be used by the body, these drugs need certain enzymes to be absorbed and used. If the enzyme cannot be used, the drug will stay in your system and increase the concentration of them in the blood.
These enzymes are needed to metabolize cholesterol-reducing drugs such as Lipitor, Zocor, and Mevacor among others. It is the same with drugs commonly used to lower blood pressure such as Norvasc, Adalat, Procardia, Isoptin, and Calan. This is also true for antihistamines and some psychiatric drugs such as Valium, Xanax, Luvox, Ambien, etc. etc.
The effect of the Grapefruit lasts 24 hours or more. Rarely, the concentrations of drugs in the bloodstream can increase to toxic levels.
If you do want to use drugs for physical conditions, do check with your pharmacist. They have a database where the drug can be checked and any interactions can be found.