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Interactions Between Medications and Grapefruit Juice
Almost ten years have past since investigators found that there are
interactions between the seemingly harmless, tangy taste of grapefruit
juice, and the metabolism of certain medications. That discovery was found
by chance during a study, which was being done to see if alcohol had any
affect on the blood pressure medication Felodipine (Plendil). One of the
researchers, a non-drinker, hoped to find a way to make alcohol taste
better. First he tried orange juice, but the taste made him look further
until he decided on double-strength grapefruit juice.
According to the study, no interaction was found between alcohol and
medication but the researchers were surprised to find that the subjects
had about three-times more felodipine in their bloodstream than predicted.
After the researchers checked with the drug company and confirmed that
the pills supplied were indeed the proper dose, a decade of grapefruit
juice and medication studies were begun. Investigations have focused on
grapefruit juice, those medications it interacts with, and specifically
the mechanism which causes the interaction. Subsequent investigations have
showed that grapefruit juice interferes with an intestinal enzyme called
CYP3A4, and can affect the absorption of at least 20 other drugs. The
amount of medication that enters your bloodstream can be more or less than
you really need. The effect of grapefruit juice varies from patient to
patient at least in part because of the wide variations in each person’s
intestinal concentration of CYP3A4.
Therefore, when you are taking medications, avoid grapefruit juice for
at least two hours before and two hours after ingesting the medication and
take your medications with water. Also remember to read the pharmacy
handout which is given with each individual drug. If there is any
interaction between your medication and grapefruit juice the handout
should alert you of this.
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Medications With Which Grapefruit Juice Should Not
Be Consumed |
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Calcium Channel Blockers |
Felodipine (Plendil)
Nimodipine (Nimotop)
Nisoldipine (Sular)
Nitrendipine
Pranidipine |
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Immunosuppressants
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Cyclosporine (Neoral) (Sandimmune)
Tacrolimus (Tacrolimus) |
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HMG-CoA Reductase
Inhibitors |
Atorvastatin (Lipitor)
Cerivastation (Baycol)
Lovastatin (Mevacor)
Simvastatin (Lescol) |
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Antihistamines |
Ebastine
Terfenadine (Seldane) |
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Psychiatric Medications |
Buspirone (BuSpar)
Carbamazepine (Tegretol) (Epitol)
Diazepam (Valium)
Midazolam (Versed)
Triazolam (Halcion) |
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Prokinetics |
Cisapride (Propulsid) |
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Others |
Metadone
Sildenafil (Viagra) |
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