Juice & Medication Doesn't Mix
Drug interaction by seeminly innocent compounds in food
Some medications can "interact" directly or indirectly with foods we eat or herbal/natural products we take.
These interactions are just as significant and potentially dangerous as drug-drug interactions, but they are more difficult to prevent as physicians usually do not have a complete list of all supplements and drugs a patient is taking. There is one common drug interaction anyone can prevent though: don’t take your medication with juice!
While juice seems such an “innocent”, even beneficial, product to consume, it can seriously alter the way in which your medication works in your body. Specifically, grapefruit juice is the problem.
Fresh as well as frozen grapefruit juice contains bioflavonoids and furanocoumarins. These two compounds are very potent inhibitors of cytochrome P450 (CYP3A4) enzymes. These enzymes are responsible for the metabolism of our drugs, and when inhibited hepatic metabolism is decreased significantly for the drugs that are substrates for CYP3A4. Some examples of medication that is metabolized by CYP3A4 include: felodipine, nifedipine, nimodipine, verapamil, terfenadine, midazolam and caffeine.
Basically, what this entire issue comes down to is the fact that more drug will be available in your blood. Less will be broken down due to decreased CYP3A4 activity, and more will be available. Drugs that have a narrow therapeutic window are especially dangerous, as it becomes much easier to reach toxic levels when metabolism is impaired. The opposite is true for pro-drugs: these need to be metabolized in order for them to become active! As such, you could be taking important medication that has absolutely no effect because of the grapefruit juice interaction, or your medication could have too much effect instead. Either way, the compounds in the juice interact with an enzyme in your body that is essential for maintaining proper therapeutic levels of the medication in your blood.
