Mixing drink and drugs: medication and fruit juice
Did you know that the effects of certain medicines can be altered by the consumption of fruit juice? When we talk about drug interactions, we usually think of side effects linked to taking multiple medications at the same time, but not about the effects our diet can have.
However, fruit juice (grapefruit in particular) can lead to problems with a lot of different molecules used in medication linked to cardiology, oncology, transplants and infections.
The risks of interaction between the agents in fruit juice and medication have been outlined in a number of studies, which we outline here… Health authorities pay special attention to these drinks (grapefruit juice in particular) and so should you.
Grapefruit juice can cause an overdose with certain medication
Up until now, only grapefruit juice was known to react strongly with some medication. There is no reduction in the effectiveness of the medication, but an increase in the frequency and severity of undesirable side effects, which is a much more significant risk than that of a decrease in the medicine’s ability to treat health problems.
Some substances present in grapefruit juice can disrupt absorption in the intestines of some medicines that the absorption is increased. The consequences of this include an increase in these medicines’ unwanted side effects, equal to an overdose.
The medicines concerned are those with a narrow therapeutic index (this means that the dose prescribed must be strictly adhered to, to avoid unwanted side-effects).
Here are the drugs affected:
- Simvastatin, and to a certain extent, atorvastatin. For simvastatin, the bioavailability is multiplied by a factor of 15, which equates to taking two week’s dosage in one go. Bioavailability for atorvastatin becomes double. The effects of drug interaction between simvastatin and grapefruit juice have been recorded in cases of rhabdomyolysis (serious deterioration of skeletal muscle);
- Immunosuppressants (tacrolimus, ciclosporine…). There is a risk of accumulation in the kidneys (nephrotoxicity);
- Cisapride, taken for Torsades de Pointes (a specific form of tachycardia, a disorder affecting the heart’s rhythm);
- An identical effect on dihydropyridines was also found. However, with the exception of lercanidipine, the consequences of this interaction with fruit juice do not have clinical side effects.
- For some other medicines, including buspirone and carbamazepine, the risk of overdose can also be increased by the absorption of grapefruit juice.
Risks with other medicines and other fruit juices
During conferences by the American Society of Chemistry in Philadelphia in 2007, David Bailey1 pointed out another potential effect of grapefruit juice. According to the results of his study, this fruit juice will inhibit the absorption of medicine containing fexofenadine (an anti-allergen).
Grapefruit juice is not the only enemy to this drug, as according to the same study, orange juice and apple juice, in amounts of about 1200ml, reduce absorption of fexofenadine by 28 and 23% respectively.
Continuing this work2, the research team have suggested that other flavonoids in certain types of fruit and vegetables can be affected. The interaction can last more the 2 hours but less than 4 hours, thus indicating that these problems can be avoided by leaving an interval of around 2-4 hours between taking medication and consuming these fruit juices. More worrying is the fact that these interactions are not confined to just the one molecule.
According to David Bailey, grapefruit juice will reduce the bioavailability of acebutolol, celiprolol, and talinolol (all involved in the treatment of hypertension), fexofenadine, and L-thyroxine (used to treat hypothyroidism) while orange juice could have the same effect on atenolol, celiprolol (antihypertensives), ciprofloxacine (antibiotic in the same family as second generation quinolones) and fexofenadine.
As these results were found in experiments and not in real-life conditions, what is the actual significance of the findings for the prescriber and patient? The interpretation of the results of one isolated study will need further confirmation.
However, it seems prudent to avoid taking medication and drinking grapefruit juice concurrently (or at least 4 hours apart).
Finally, the hypothesis put forward by David Bailey in this study must not overshadow the risk of drug interaction linked to grapefruit juice. It is most important to remember that this interaction can lead to an overdose when taking the medication listed in this article. If you have doubts or questions, do speak to your health professional.
1. “Naringin is a major and selective clinical inhibitor of organic anion-transporting polypeptide 1A2 (OATP1A2) in grapefruit juice,” Bailey DG et al., Clinical Pharmacology & Therapeutics, 2007; 81:495-502.)
2. “Fruit juice inhibition of uptake transport: a new type of food-drug interaction,” David Bailey – British Journal of Clinical Pharmacology, Volume 70, Issue 5, pages 645-655, November 2010
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