Pomelo is rich in nutrients, containing various essential substances for the human body, such as vitamins B and C and minerals.

Pomelo also contains furanocoumarins, a type of natural organic compound. The most common types are psoralen and bergapten, which are furan-ring fused at positions 6,7 and 7,8 of coumarin, respectively.

Their derivatives are known as linear furanocoumarins and angular furanocoumarins.

However, research indicates that pomelo juice can affect the metabolism of various common medications, potentially leading to severe toxic side effects. Today, we will discuss the pros and cons of combining pomelo juice with commonly used medicines for the urinary system.

The initial research dates back to the late 1980s when researchers discovered that pomelo increased the bioavailability of the antihypertensive drug nifedipine. Currently, it has been found that pomelo can affect around 90 different drugs, with more than 40 of them being significantly impacted. Moreover, the higher the intake of pomelo, the higher the occurrence of adverse drug reactions.

Ms. Shiew Mei Huang, Director of the Office of Clinical Pharmacology at the U.S. Food and Drug Administration (FDA), stated that most drugs react with specific components of pomelo, causing an increase in the amount of some drugs entering the bloodstream. When the concentration of drugs in the blood exceeds normal levels, the side effects and adverse reactions of the drugs become highly dangerous to the human body.

For example, when patients take statin drugs for cholesterol reduction with pomelo juice, the statins accumulate in their bloodstream, significantly increasing the risk of liver damage and muscle breakdown, leading to kidney failure.

Recent studies have also found that, apart from causing some drugs to be absorbed excessively, pomelo juice may lead to insufficient absorption of other medications. For instance, taking fexofenadine, an antihistamine for seasonal allergy relief, with pomelo juice reduces its absorption in the body. Even with other juices like orange or apple juice, it still lowers the body's absorption of fexofenadine.

Therefore, the drug instructions for fexofenadine explicitly state, "Do not take with fruit juices."

The reason pomelo juice can cause both excessive and insufficient drug absorption lies in the way drugs are metabolized. Many drugs are broken down and metabolized by an essential enzyme in the human small intestine, CYP3A4.

Some components in pomelo juice inhibit the effectiveness of this enzyme, preventing the timely breakdown and excretion of these drugs. Drugs that are not metabolized enter the bloodstream and linger in the body longer, causing potentially dangerous levels of medication.

Making the situation more complex, the amount of the CYP3A4 enzyme in the small intestine varies from person to person. Some individuals have a significant amount of CYP3A4, while others have little. Therefore, the impact of pomelo juice on drug absorption when taking the same medication varies among different individuals.

As for drugs that require the assistance of transport proteins to be delivered to target cells and absorbed by the body, the components in pomelo inhibit these proteins, resulting in insufficient drug absorption and consequently reducing the effectiveness of the medication.

Even if taken a few hours before or after medication, the FDA warns that significant risks may still exist. Therefore, when taking these medications, avoiding them altogether or minimizing the intake of pomelo juice or fresh pomelo is advisable.

Currently, the FDA has mandated that the prescribing information for some prescription drugs must explicitly state that the drug should not be taken simultaneously with pomelo juice or fresh pomelo. The FDA continues to investigate other medications that should not be taken concurrently with pomelo, and once identified, adjustments to the prescribing information will be required.