Fruit juice 'could affect drugs'

By KomodoMK · Aug 22, 2008 · ·
  1. KomodoMK
    Drinking fruit juices may not be as healthy an option as thought - they could reduce the effectiveness of some medicines, it is being claimed.

    Research presented at a US conference suggested a chemical in grapefruit juice could stop anti-allergy drugs being absorbed properly.

    A University of Western Ontario team said oranges, and possibly apples, had similar ingredients.

    Grapefruit juice is already known to interfere with blood pressure drugs.

    Some medications carry a warning that taking them alongside grapefruit juice could cause an overdose.

    However, the latest finding, presented at the American Chemical Society conference in Philadelphia, points to a different problem with researchers saying it was "the tip of the iceberg".

    In this case, he found that the grapefruit juice had the reverse effect on fexofenadine, an antihistamine drug, making it less potent rather than more potent.

    Volunteers took the drug with either a single glass of grapefruit juice, or just water.

    When it was taken with juice, only half the drug was absorbed, potentially reducing its effectiveness.

    Orange warning

    Researchers believe that an active ingredient of the juice, naringin, appears to block a mechanism which moves drug molecules out of the small intestine into the bloodstream.

    Study author Dr David Bailey said that orange and apple juices appeared to contain naringin-like substances which might have a similar effect.

    "Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs undergoing intestinal uptake transport.

    "The concern is loss of benefit of medications essential for the treatment of serious medical conditions."

    So far, the three types of juice have been found to affect etoposide, a chemotherapy drug, some beta-blocker drugs used to treat high blood pressure, and cyclosporine, taken by transplant patients to prevent rejection of their new organs.

    However, Dr Bailey said: "This is just the tip of the iceberg - I'm sure we'll find more and more drugs that are affected this way."

    Colette McCready, from the National Pharmacy Association, said: "The effect of grapefruit juice on some medicines is well established and where this applies it is clearly detailed in Patient Information Leaflets.

    "Pharmacists will usually draw this matter to patients' attention when dispensing their medicines. This new research showing that apple and orange juice may enhance or reduce the effects of some medicines is interesting but it is only one study.

    "Usually further research is needed to establish that these interactions are significant."

    Professor James Ritter, a clinical pharmacologist at King's College London, said: "The observation is very interesting. It will need more work to establish how important such interactions are in clinical practice and for what drugs and juices."


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  1. Zentaurus41
    This has more or less been known for many years as Grapefrit juice contains the P450 enzye which inhibits the metabolism of opiates. Which I think is were the myth about taking orange juice with lsd probably comes from.

    Though Orange juice is an acid which can alter the ph of the stomach and so changeing the rate of absorbtion.
  2. chaton
    AW: Re: Fruit juice 'could affect drugs'

    So can aple juice also because it is also acid, not so much as orange juice.
  3. Zentaurus41
    I think it all depends on the pH, here is some information which may help :

    Most drugs are weak organic acids or bases, existing in un-ionized and ionized forms in an aqueous environment. The un-ionized form is usually lipid soluble (lipophilic) and diffuses readily across cell membranes. The ionized form has low lipid solubility (but high water solubility—ie, hydrophilic) and high electrical resistance and thus cannot penetrate cell membranes easily. The proportion of the un-ionized form present (and thus the drug's ability to cross a membrane) is determined by the pH and the drug's pKa(acid dissociation constant). The pKa is the pH at which concentrations of ionized and un-ionized forms are equal. When the pH is lower than the pKa, the un-ionized form of a weak acid predominates, but the ionized form of a weak base predominates. Thus, in plasma (pH 7.4), the ratio of un-ionized to ionized forms for a weak acid (eg, with a pKa of 4.4) is 1:1000; in gastric fluid (pH 1.4), the ratio is reversed (1000:1). Therefore, when a weak acid is given orally, most of the drug in the stomach is un-ionized, favoring diffusion through the gastric mucosa. For a weak base with a pKa of 4.4, the outcome is reversed; most of the drug in the stomach is ionized. Theoretically, weakly acidic drugs (eg, aspirin) are more readily absorbed from an acid medium (stomach) than are weakly basic drugs (eg, quinidine). However, whether a drug is acidic or basic, most absorption occurs in the small intestine because the surface area is larger and membranes are more permeable
  4. Bajeda
    The orange juice and LSD thing has been discussed elsewhere, and it appears to not entirely be a myth.
  5. therustedgauge
    OJ & Acid = Incorrect
    Grapefruit & Acid = Correct. :)

    the different complexities of the acid is where it starts. Also Benzo's (xanax, klonopin) are affected by Grapefruit... can increase the effects like, respiratory suppression & lethargy etc.
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