Published: 5 September 2024

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Medicines and food: interacting combinations

Published: 5 September 2024
Prescriber Update 45(3): 59–61
September 2024

This article highlights some foods and food groups that have the potential to interact with medicines. It is not a comprehensive list.

Pharmacokinetic interactions between medicines and foods

Some foods may affect the absorption, distribution, metabolism or excretion of a medicine.¹

Fruit and fruit products

Fruit and their products contain diverse chemical compounds, some of which affect the metabolism and elimination of orally administered medicines. For example, naringin (a flavonoid) and bergamottin and 6’,7’-dihydroxybergamottin (furanocoumarins) inhibit the cytochrome P450 isoenzyme, CYP3A4.

Other chemical compounds in fruit inhibit organic anion-transporting polypeptides (membrane transporter proteins) and P-glycoprotein (efflux transporter).²

Grapefruit juice inhibits intestinal CYP3A4, and so is expected to increase the exposure of medicines metabolised by this enzyme, such as statins and calcium channel blockers.² An interaction with grapefruit juice is particularly relevant for medicines that have a narrow therapeutic index (eg, ciclosporin) or with poor oral bioavailability (eg, felodipine).¹

Other fruits reported to interact with some medicines include orange, pomelo and cranberry.²

Food rich in divalent ions

Food rich in divalent ions (eg, calcium and magnesium), such as milk, cheese and yoghurt, may form chelate complexes with certain medicines. These complexes may then decrease the absorption and bioavailability of the medicine.³

Because they form these chelate complexes, fluoroquinolones (eg, oral ciprofloxacin) should not be taken concurrently with dairy products or mineral fortified drinks (eg, milk, yoghurt, calcium fortified orange juice). However, if these products are ingredients of meal, they will not significantly affect ciprofloxacin absorption.⁴

Dairy products may also affect oral iron⁵ and tetracycline³ absorption.

Pharmacodynamic interactions between medicines and food

Consuming certain foods may have an additive, synergistic or antagonistic effect with a medicine.³

Food rich in tyramine

Some foods are high in tyramine, such as mature cheese, pickled herring, broad bean pods, meat extracts (eg, Bovril) and yeast extract (eg, Marmite and Vegemite).

Tyramine is a trace monoamine with sympathomimetic properties. In comparison to the monoamine neurotransmitters (noradrenaline, adrenaline, dopamine and serotonin), tyramine levels are relatively low in the body. However, ingestion of dietary tyramine can displace the monoamine neurotransmitters, particularly noradrenaline, from pre-synaptic storage vesicles, releasing them into the circulation. Increased noradrenaline causes vasoconstriction, increased heart rate and a rise in blood pressure.⁶

The monoamine oxidase (MAO) enzyme metabolises monoamines. In normal circumstances, the A form of this enzyme (MAO-A) metabolises circulating noradrenaline so that it does not accumulate to dangerous levels. MAO-A also metabolises tyramine before it can release noradrenaline into the circulation. However, MAO inhibitor (MAOI) medicines significantly reduce the body’s capacity to metabolise tyramine. Patients taking MAOIs who eat a high-tyramine meal may be at risk of hypertensive crisis (severely elevated blood pressure).⁷

Irreversible and non-selective MAOIs, such as tranylcypromine, have the greatest risk of serious interactions, and patients taking these medicines should completely avoid tyramine-rich food.⁸ In contrast, patients taking reversible MAOIs, such as moclobemide or linezolid, should avoid consuming large amounts of tyramine-rich food.^9,10

Diet rich in Vitamin K

Vitamin K-rich food includes broccoli, brussels sprouts, green leafy vegetables and liver.

Warfarin blocks production of vitamin K-dependent blood clotting factors to produce an anticoagulant effect. Sudden changes in diet that significantly increase or decrease the intake of Vitamin K-rich foods may affect control of anticoagulation. Inform patients taking warfarin to seek medical advice making any major changes to their diet.¹¹

Further information

For information on potential food–medicine interactions and their management (eg, avoiding concurrent use or separating intake), refer to:

• section 4.5 of the medicine data sheets
• the New Zealand Formulary interaction checker (based on Stockley’s Interaction Alerts).

See also previous Prescriber Update articles on food and medicine interactions.

• Can I have a drink with that? (alcohol)
• Liquorice – All sorts of side effects and interactions (liquorice)
• Fruit interactions with common medicines (fruit and fruit products)
• Warfarin: eat, drink and be wary (interactions with warfarin)

Refer patients to the Medicines and diet section of Healthify for more information.

References

1. Petric Z, Žuntar I, Putnik P, et al. 2020. Food-drug interactions with fruit juices. Foods 10(1): 33. DOI: 10.3390/foods10010033 (accessed 17 July 2024).
2. Preston CL, Jones S and Sandhu H. 2014. How fruit juice interacts with common medicines. Pharmaceutical Journal 293(7831): 369-72. URL: pharmaceutical-journal.com/article/ld/how-fruit-juice-interacts-with-common-medicines (accessed 17 July 2024).
3. Bushra R, Aslam N and Khan AY. 2011. Food-drug interactions. Oman Medical Journal 26(2): 77-83. DOI: 10.5001/omj.2011.21 (accessed 17 July 2024).
4. Viatris Ltd. 2022. Cipflox New Zealand Data Sheet 16 June 2022. URL: www.medsafe.govt.nz/profs/datasheet/c/cipfloxtabinf.pdf (accessed 17 July 2024).
5. Viatris Ltd. 2023. Ferodan New Zealand Data Sheet 13 September 2023. URL: www.medsafe.govt.nz/profs/datasheet/f/ferodansol.pdf (accessed 17 July 2024).
6. Burns C and Kidron A. 2024. Biochemistry, Tyramine. In: StatPearls [Internet] updated 10 October 2022. URL: pubmed.ncbi.nlm.nih.gov/33085344/ (accessed 17 July 2024).
7. Stahl SM and Felker A. 2008. Monoamine oxidase inhibitors: a modern guide to an unrequited class of antidepressants. CNS Spectrums 13(10): 855-70. DOI: 10.1017/s1092852900016965 (accessed 17 July 2024).
8. Boucher & Muir (NZ) Ltd t/a Mercury Pharma (NZ). 2022. Parnate New Zealand Data Sheet 29 November 2022. URL: www.medsafe.govt.nz/profs/datasheet/p/Parnatetab.pdf (accessed 17 July 2024).
9. Viatris Ltd. 2023. Aurorix New Zealand Data Sheet 24 May 2023. URL: www.medsafe.govt.nz/profs/datasheet/a/aurorixtab.pdf (accessed 17 July 2024).
10. Pfizer New Zealand Limited. 2023. Zyvox New Zealand Data Sheet 18 September 2023. URL: www.medsafe.govt.nz/profs/datasheet/z/Zyvoxinjtabsusp.pdf (accessed 17 July 2024).
11. GlaxoSmithKline NZ Limited. 2023. Marevan New Zealand Data Sheet 14 March 2023. URL: www.medsafe.govt.nz/profs/datasheet/m/Marevantab.pdf (accessed 17 July 2024).