Antihistamines and Citrus Fruits: What You Need to Know

Antihistamines and citrus fruits

Hello, Doctor Gao.
Recently, my allergic condition has worsened, and my doctor advised me to take antihistamines long-term.
The medication label states that antihistamines should not be taken with grapefruit.
I would like to ask: does this mean that antihistamines should not be taken at the same time as grapefruit, or should grapefruit be avoided throughout the entire duration of the medication? Additionally, my family's orchard is starting to bear citrus fruits, such as pomelo, shiranui, lemons, and oranges, and later we will have varieties like ponkan and tangerines.
These fruits seem to belong to the same group; should I consider them as contraindicated like grapefruit? Thank you very much!

Nongyou, 40~49 year old female. Ask Date: 2013/09/28

Dr. Gao Jiankai reply Internal Medicine

Hello, farmer.
Thank you for your question.
First of all, grapefruit contains compounds that inhibit the liver's metabolism of certain medications, leading to increased concentrations of these drugs in the body.
If the increase exceeds the therapeutic dose significantly, it can result in adverse side effects.
The medications at risk include antihistamines, which you inquired about today, as well as lipid-lowering agents, antifungal medications, some antihypertensives, and certain immunosuppressants.

In addition to grapefruit, other citrus fruits can also pose similar risks, such as the ones you mentioned.
However, grapefruit has a higher concentration of these compounds, and since grapefruit is derived from pomelo, the effects of pomelo may be similar to grapefruit, although there is no literature comparing the two, so I cannot specify the extent of the impact.
Other citrus fruits, including tangerines, sweet oranges, lemons, and mandarins, are likely to have a lower impact.
That said, literature indicates that due to drug-drug or drug-food interactions, many antihistamines that could potentially cause toxicity have been withdrawn from the market, and many hospitals no longer stock them.
Currently available antihistamines have a high safety profile, and the dosages prescribed by physicians are often well below the safe limits of the medications themselves.
Therefore, even if you consume some citrus fruits like grapefruit for a short period, leading to increased drug concentrations in your body, it is unlikely to result in severe side effects.

For safety's sake, you may want to consult your physician to understand the current dosage and inquire about any risks associated with taking grapefruit juice concurrently.
This would provide you with more peace of mind.
However, the above statements primarily pertain to medications with a high safety profile, such as antihistamines.
For the other types of medications mentioned, it is advisable to avoid consuming grapefruit and pomelo together to prevent potential side effects.

Best regards from the Allergy, Immunology, and Rheumatology Department of Changhua Hospital, Ministry of Health and Welfare.

Reply Date: 2013/09/28

More Info

When it comes to antihistamines and citrus fruits, particularly grapefruit, there are important considerations to keep in mind. Grapefruit is known to interact with various medications, including certain antihistamines, due to its ability to inhibit enzymes in the liver that are responsible for drug metabolism. This can lead to increased levels of the medication in the bloodstream, potentially causing adverse effects.

To address your specific questions, it is crucial to understand that the warning against consuming grapefruit while taking antihistamines is not just about timing. It is generally advised to avoid grapefruit entirely during the course of treatment with these medications. This is because the effects of grapefruit on drug metabolism can last for an extended period, sometimes up to 24 hours or more after consumption. Therefore, even if you consume grapefruit juice or the fruit a few hours before taking your antihistamine, it could still affect how your body processes the medication.

As for other citrus fruits, such as pomelo, lemons, and oranges, the situation is somewhat different. While grapefruit has a significant impact on drug metabolism due to its high levels of certain compounds, other citrus fruits typically have a much lower risk of interacting with medications. However, pomelo (which is closely related to grapefruit) may also have similar effects, so it is advisable to exercise caution with it as well. On the other hand, fruits like lemons and oranges are generally considered safe to consume while taking antihistamines, as they do not have the same inhibitory effects on drug metabolism.

Given that you are experiencing severe allergic reactions and are required to take antihistamines long-term, it is essential to consult with your healthcare provider regarding your diet. They can provide personalized advice based on your specific medications and health condition. It is also a good practice to read the labels on your medications and follow any dietary restrictions provided by your pharmacist or doctor.

In summary, avoid grapefruit and possibly pomelo while taking antihistamines, and consult your healthcare provider about the safety of consuming other citrus fruits. Maintaining open communication with your healthcare team will help ensure that you manage your allergies effectively while minimizing the risk of adverse drug interactions.

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