This interaction can be dangerous. With most drugs that interact with grapefruit juice, the juice increases the absorption of the drug into the bloodstream. When there is a higher concentration of a drug, you tend to have more adverse events.
For example, if you drink a lot of grapefruit juice while taking certain statin drugs to lower cholesterol, too much of the drug may stay in your body, increasing your risk for liver damage and muscle breakdown that can lead to kidney failure.
Drinking grapefruit juice several hours before or several hours after you take your medicine may still be dangerous, so it’s best to avoid or limit consuming grapefruit juice or fresh grapefruit when taking certain drugs.
With Supplements:
Grapefruit juice increases the absorption, bioavailability, and potency of nutrients due to the bergamottin content of grapefruit temporarily blocking some types of Cytochrome P-450 enzymes (especially CYP3A4 enzyme) in the gastrointestinal tract. Like all Cytochrome P-450 enzymes, CYP3A4 is responsible for the (phase I) detoxification of various substances in the intestines and liver. This inhibitory effect of Grapefruit juice may last for up to 48 hours after ingestion. Conclusion: In my opinion, the effect of grapefruit or grapefruit juice is positive, favoring nutrient potency effects in human metabolism with most supplements, not all. Taken with COQ10 it will have a fat burning affect for hours.