Action: naringin interferes with enzymatic activity in the intestines and, thus, with the breakdown of certain drugs, resulting in higher blood levels of the drug. A number of drugs that are known to be affected by the naringin in grapefruit include calcium channel blockers, estrogen, sedatives, medications for high blood pressure, allergies, AIDS, and cholesterol-lowering drugs. Caffeine levels and effects of caffeine may also be extended by consuming grapefruit or grapefruit juice. While the effect of naringin on the metabolism of a drug can increase the drug's effectiveness, it can also result in dosages that are inadvertently too high. Therefore, it's best not to take any drugs with grapefruit juice unless the interaction with the drug is known..