Transplant patients know that grapefruit should not be consumed with immunosuppressive drugs (anti-rejection). Nephrologists and dieticians always inform patients after a transplant. For patients who have spent several years on dialysis, depriving themselves of grapefruit after the transplant is a minor inconvenience. Various research and articles from different blogs and health websites highlight that many other drugs than immunosuppressants are contraindicated with the consumption of grapefruit. Grapefruit has many benefits, but when consumed with certain medications can have adverse effects on the patient. In this publication, we shall give insight into why grapefruit is forbidden when taking some medications.

Why Is Grapefruit Prohibited When Taking Certain Medications?

The drugs we swallow are eliminated and transformed by enzymes present in the small intestine and colon as well as in liver cells. The drug is, therefore, degraded successively at these different levels, and only a percentage of the active principle of the medicine reaches the bloodstream. However, certain chemicals present in grapefruit (furanocoumarins) have the power to block the action of enzymes, and the dose that enters the blood is then much higher than expected.

This problem concerns grapefruit in all its forms, consumed whole or squeezed in juice, or based on concentrate, frozen or cooked, pomelo, and also bitter oranges. Sweet oranges do not have this risk because they do not contain furanocoumarins.

Even at low doses, grapefruit should not be taken with anti-rejection drugs. The age of patients also plays a role: from 45 years of age, and the risk is higher. Currently, more than 85 drugs are known to interact with grapefruit, and 43 of them can cause serious side effects—heart problems, rhabdomyolysis, myelotoxicity, respiratory depression, gastrointestinal bleeding, nephrotoxicity. Only oral medications are affected. Taking grapefruit when undergoing herbal medication like is “hua Laksiam” really effective (ฮั้วลักเซียมดีจริงไหม ,which is the term in Thai), i guess not.