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nifedipine and grapefruit
  1. #1
    withwhomilivalie is offline Junior Member
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    Default nifedipine and grapefruit

    I'm taking a new medication for blood pressure that is called Nifedipine Extended Release. It says you can't eat grapefruits or grapefruit juice within 2 hours of taking the pill. Why is this?

  2. #2
    ariadaun Guest

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    According to the product information sheet for nifedipine:
    Co-administration of nifedipine with grapefruit juice resulted in approximately a 2-fold increase in nifedipine AUC and Cmax with no change in half-life.

    In other words, grapefruit plus nifedipine would be like taking twice the dose of nifedipine.

    There are a lot of food-drug interactions, and Rx-OTC drug interactions that behave similarly. Sometimes the foods that are contraindicated can cause the drug potentcy to increase or decrease (sometimes much greater than 2x). Sometimes it can completely neutralize (for lack of a better term) the medication entirely. Some foods or OTCs can cause Rx drugs to be absorbed quicker, slower, or not at all.

    As far as why grapefruit interacts with this particular drug in this way, I can't give you a definite answer there. I would think it is due to a chemical reaction between them or the acidity of the grapefruit juice could cause the nifedipine to be absorbed quickly in the stomach, rather than later in the digestive tract.

    After re-reading your post, I see you are on an extended release pill. Extended release meds, if I remember this correctly, are absorbed in the intestine rather than the stomach and should usually be taken on an empty stomach to aid in the pill reaching the intestine intact where it slowly breaks down and is absorbed over time. With the acid of grapefruit juice, I would assume this would speed the breakdown of the pill, negating its extended release properties, causing the medication to be absorbed either in the stomach or all at once upon reaching the intestines.

  3. #3
    withwhomilivalie is offline Junior Member
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    Thank you

    My drug info sheet just says they interact in a negative way. It didn't say why. Thanks for the info.

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