Grapefruit, also known as grapefruit and wendan, belongs to the citrus category, which also includes oranges, lemons and other fruits with similar ingredients. More and more drugs have been found to cause adverse reactions when taken with grapefruit juice, and the culprit is a chemical contained in grapefruit – furanocoumarin. Furanocoumarins, which are abundant in grapefruit, can inhibit the activity of enzymes that break down drugs in the body, resulting in a doubling of the amount of the drug entering the bloodstream. Pharmacologists pointed out that with a cup of grapefruit juice and a dose of certain drugs, sometimes equivalent to taking 20 tablets of this drug and a glass of water, which inadvertently increased the dose of drugs, which led to the cure of the drug into a “poison”. Once the study was published, it immediately caused a lot of people to worry. Grapefruit juice and grapefruit fruits produce toxic side effects of 85 kinds of drugs. Such as: nifedipine (hypertension / angina), domperidone / morpholine (antiemetic / anti-nausea), erythromycin (antibiotics), dasatinib (leukemia), erlotinib (lung and pancreatic cancer), everolimus (renal cell carcinoma), lapatinib (breast cancer), nilotinib (leukemia), pazopanib (renal cell carcinoma), sunitinib (kidney / gastrointestinal cancer), verofinil (skin cancer) , eplerenone (heart failure), oral alfentanil (painkiller), sofenacin (urinary frequency/incontinence), silodosin (prostate hyperplasia), etc. Transplant recipients taking immunosuppressive drugs (tacrolimus, cyclosporine, rapamycin) along with grapefruit juice have been shown to increase drug concentrations. This is mainly because grapefruit juice can specifically reduce the level of CYP3A4 enzyme in the epithelial cells of the small intestine, and the immunosuppressive drugs taken need to be metabolized by this enzyme, thus reducing the metabolism of the above immunosuppressive drugs before they are absorbed into the blood in the small intestine, resulting in a significant increase in blood concentration. It is recommended to take grapefruit juice to increase the concentration of immunosuppressive drugs under the guidance of a doctor, but some doctors do not recommend the use of grapefruit juice to increase the blood concentration of immunosuppressive drugs, because the effect of grapefruit juice on each individual is different, in addition, although grapefruit juice can increase the concentration of drugs, but the effect is unstable, easy to make the blood concentration fluctuate, affecting the function of transplanted organs. At present, the principle of using drugs and some foods to increase the concentration of immunosuppressants is that it is only recommended when the dose of immunosuppressants has been used to lead to the maximum dose, but the blood concentration is still not up to standard, and the first choice is to protect the liver tablets, five ester soft capsules and other drugs. The adjuvant treatment of uniformly lowering the dosage of immunosuppressants and adding to increase the concentration of drugs, because the individual body’s response to the drug varies greatly, thus increasing the difficulty of clinical adjustment of immunosuppressants, resulting in drug adjustment cannot be carried out as scheduled.