Grapefruit juice has become notorious since the 1991 discovery that drinking grapefruit juice can change the blood levels of certain medications (The Lancet, Feb. 2, 1991). It turns out, however, that grapefruit juice and its effects on drug metabolism are just the tip of the iceberg. This topic is far more complicated than most of us imagine. It is no wonder this couple has become embroiled in a disagreement.
The Citrus Juice Quarrel:
Q. I have understood that grapefruit juice generally should not be used to take medicine. My wife believes that orange juice is also dangerous. She is urging me not to take my pills with orange juice.
Isn’t Grapefruit Juice Different from Orange Juice?
I understand that grapefruit juice contains an ingredient that orange juice does not and that is what interacts adversely with medicine. This is now becoming a major issue for us; can you resolve it?
A. As with most marital disputes, the answer to your question is complicated.
The Grapefruit Effect:
Scientists have known for 25 years that grapefruit juice has a special ability to increase blood levels of certain medications, including the hypertension drug felodipine, cholesterol-lowering meds such as atorvastatin and simvastatin and the anti-anxiety agent buspirone. It does this by inhibiting the intestinal enzyme CYP3A4 that metabolizes many medicines. The increased blood levels can make side effects more severe.
The only other fruits that act like grapefruit are Seville (sour) oranges and pomelos.
What About Orange Juice?
Ordinary orange juice and apple juice can affect other medications in a completely different way (Journal of Clinical Pharmacology, online June 10, 2015). Instead of inhibiting CYP3A, these fruit juices inhibit the compounds that help move certain medications into tissues and cells.
Which Drugs Are Affected by Apple or Orange Juice?
The affected drugs include aliskiren (Tekturna), fexofenadine (Allegra) and atenolol (Tenormin), most notably. The impact is to lower tissue levels and effectiveness.
The grapefruit effect can last for a few days, while orange juice activity disappears within a few hours. Whether or not you need to avoid taking your medication with grapefruit or orange juice depends which drug you are taking. We hope this helps resolve the disagreement between the two of you.