Grapefruit Juice and
Drug Interactions

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

From June 2001 Issue of Nutrition Science News

by Anthony Almada

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Two popular morning beverages, orange and grapefruit juices, may cause adverse prescription drug reactions. Several compounds found in both juices inhibit normal detoxification and metabolic processes in the intestines and liver. [1, 2] As a result, the body absorbs an increased amount of some drugs. [3, 4] Combining grapefruit juice with drugs that are poorly absorbed or metabolized by specific enzymes in the cytochrome P450 family—cyclosporine, felodipine, verapamil, triazolam and terfenadine—can result in side effects.

One of the identified culprits in grapefruit juice is the flavonoid naringenin, which is also found in orange juice but at one-tenth the concentration. Recent studies show that drinking either juice increases blood naringenin, [5] suggesting orange juice also may inhibit the detoxification process. However, no studies have been done to determine whether orange juice leads to drug interactions, so the takeaway message to give customers is to be careful what they use to wash down certain drugs.

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Anthony Almada is a nutritional and exercise biochemist and has collaborated on more than 50 university-based clinical trials. He is the co-founder of EAS and founder and chief scientific officer of IMAGINutrition.

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References:

1. Bailey DG, et al.
   Grapefruit juice-drug interactions.
   Br J Clin Pharmacol 1998;46:101-10.
   

2. Guo LQ, et al.
   Role of furanocoumarin derivatives on grapefruit juice-mediated inhibition of human CYP3A activity.
   Drug Metab Dispos 2000;28:766-71.
   

3. Bistrup C, et al.
   Effect of grapefruit juice on Sandimmun Neoral absorption among stable renal allograft recipients.
   Nephrol Dial Transplant 2000;16:373-7.
   

4. Ho PC, et al.
   Effect of grapefruit juice on pharmacokinetics and pharmacodynamics of verapamil in healthy volunteers.
   Eur J Clin Pharmacol 2000 Dec;56(9-10):693-8.
   

5. Erlund I, et al.
   Plasma kinetics and urinary excretion of the flavanones naringenin and hesperetin in humans after ingestion of orange juice and grapefruit juice.
   J Nutr 2001;131:235-41

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