For this reason, it is important for people to know that taking Allegra with various fruit juices, especially orange and grapefruit juice, reduces the absorption of Allegra by more than a third, making the medicine less effective.
Allegra, when taken orally, depends on specialized receptors on cells within the small intestines, called organic anion transporting polypeptides (OATPs), to absorb the medicine into the body. When various fruit juices are present in the small intestines, especially grapefruit, apple or orange juice, these OATPs are unable to absorb Allegra into the body. This effect seems to occur with soft drinks with as little as 5 percent fruit juice. Taking Allegra with fruit juice may decrease the absorption by nearly 40 percent or more, making the medicine far less effective against the treatment of allergy symptoms.
Therefore, the package insert for prescription Allegra, as well as the patient instructions for OTC Allegra, recommend not taking this medication with fruit juices. I would take this a step further and recommend that a person not eat or drink any product containing fruit or fruit juice for a couple of hours before or after taking Allegra. Doing so would dramatically reduce the effectiveness of the drug and leave a person suffering with uncontrolled allergy symptoms.
Read more about the use of antihistamines for the treatment of allergies.
Bailey G. Fruit Juice Inhibition of Uptake Transport: A New Type of Food-Drug Interaction. Br J Clin Pharmacol. 2010 Nov;70(5):645-55.
Kalliokoski A, Niemi M. Impact of OATP Transporters on Pharmacokinetics. British Journal of Pharmacology (2009) 158, 693–705.
Allegra package insert. Sanofi Aventis Corporation. Website accessed May 22, 2011.
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