PEN® eNews 15(4) April 2025 - Food-Drug Interactions
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® eNews is a monthly e-newsletter shared with the global PEN Community and created to help dietitians position themselves as leaders in evidence-based nutrition practice. In addition, users of the PEN System will find articles on the new evidence, resources and features available and how to maximize one's use of PEN.
Do Non-Warfarin Anticoagulant Medications Still Interact With Grapefruit?
It's well known that warfarin interacts with many foods and supplements, but what about anticoagulant medications other than warfarin? Do these alternate medications require less dietary planning than warfarin does, or do they interact with just as many foods? PEN recently investigated these questions.
The Question
Which foods/ dietary supplements interact with warfarin or other anticoagulant medications?
Recommendation
Although non-vitamin K antagonist oral anticoagulants (NOACs) offer an alternative to warfarin therapy, their interactions with food and dietary supplements have rarely been examined in human in vivo studies. Given the theoretical potential of foods and supplements that strongly potentiate or inhibit P-glycoprotein or CYP3A4 metabolism to adversely interact with NOACs, individuals taking NOACs would be prudent to avoid foods and supplements that strongly potentiate or inhibit these mechanisms and to only consume foods and supplements with moderate or minor theoretical effects under close supervision.
Remarks
Examples of NOACs include dabigatran, rivaroxaban, apixaban and edoxaban.
To see the full practice question, including the Evidence Statements, Remarks and References, click here.
Which Fruits and Juices Commonly Interact With Medications?
Some fruit and juices interact significantly with medications. Which ones should dietitians tell their patients/ clients to worry about? PEN recently investigated this question.
The Question
Are there any fruit or fruit juices that should be avoided when taking medications?
Recommendation
Drugs that can be expected to interact with grapefruit and grapefruit juice are drugs that:
The magnitude of this response will vary widely across the population and may or may not be clinically important. Seville orange and pomelo juice also affect CYP3A4 metabolism, although these fruits were not seen to have as many interactions or as large effects as grapefruit juice did.
If all three of the above criteria are met, it would be prudent for individuals to avoid grapefruit and grapefruit juice or to switch to an alternate drug (if possible/ preferred). If one or two of the above criteria are met, it would be prudent to allow grapefruit and grapefruit juice consumption as long as side-effects are monitored closely.
Although non-grapefruit fruits and juices can interact with some medications, none have been found to have deadly impacts the way that grapefruit can.
To see the full practice question, including the Evidence Statements, Remarks and References, click here.
Does a Ketogenic Diet Affect Medication Efficacy?
We know that some medications should be taken with or without food - but does the type of food matter? For individuals consuming a very low carbohydrate (ketogenic) diet, should considerations be made to their medication type and dosage? PEN recently investigated these questions.
The Question
How does following a ketogenic diet affect the efficacy and safety of certain medications (e.g. anti-epileptic, anti-diabetic, cardiovascular)?
Recommendation
It is possible that a ketogenic diet may interfere with the efficacy and increase the adverse effects of some medications. Although some effects may be positive (e.g. may augment the antipsychotic effects of some psychiatric medications), individuals who take medications chronically should not follow a ketogenic diet without first discussing the possible interactions with a specialist.
Remarks
It should be noted that KD side-effects (e.g. constipation, dehydration, fatigue, acidosis) can lead to discontinuation of the diet, especially in children and individuals with autism spectrum disorder or bipolar disorder.
See Additional Content: Nervous System-Pediatric Epilepsy: Ketogenic Diet Knowledge Pathway
To see the full practice question, including the Evidence Statements, Remarks and References, click here.
Thank You to Our Past Contributors!
If you wrote for PEN years ago, you still get credit for your contribution on the website!
When viewing a Practice Question or another part of a Knowledge Pathway, there is directory on the right-hand side of the page. The final item is called “Pathway Contributors”. If you did not write the most recent content available in PEN but did contribute to a topic in the past, your name will be listed under “past” pathway contributors!
Thank you for your hard work and support!
Did You Know?
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Hover over any of the pictures, and you’ll see text appear. Click any button to go to the corresponding section!
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Happy learning!
PEN eNews
April 2025 Volume
15 (4)
A Publication of the PEN® System Global Partners,
a collaborative partnership between International Dietetic Associations.
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