Friday, January 28, 2011

Grapefruit juice: Dangerous medication interactions

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Grapefruit juice: Dangerous medication interactions
Researchers have known for twenty years that taking medications with grapefruit juice can increase the absorption of certain drugs — with the potential for turning normal doses into toxic overdoses.

However, a few years ago a study found that consuming grape, apple or even orange juice can affect the absorption of other drugs, potentially wiping out their beneficial effects and in some cases causing toxic side effects.

The juice from these fruits often interferes with the way the body metabolises some medications. Usually enzymes lining the small intestines destroy a certain portion of the medication taken, causing only a limited amount from making its way to your blood stream.
However, grapefruit juice wields the power to prevent your intestinal lining from working appropriately. Grapefruit is metabolised in the liver by an enzyme that also metabolises close to half the drugs consumed by people today. What happens is when the grapefruit keeps the enzyme busy, it is unable to break down the drugs, causing the drug to accumulate in the bloodstream. Depending on the drug , an individual will have a variety of side effects due to the “overdose”.

The first controlled human studies on this potentially dangerous interaction took place in 2008 by University of Western Ontario, headed up by David G. Bailey, Ph.D., a professor of clinical pharmacology.

According to the study grapefruit, orange and apple juice have been shown to lower the absorption of etoposide, an anticancer agent; also certain beta blockers (atenolol, celiprolol, talinolol) used to treat high blood pressure and prevent heart attacks; cyclosporine, a drug taken to prevent rejection of transplanted organs; and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole). Medications taken for depression, seizures and abnormal heart rhythms were also listed as likely candidates.

A Few Examples of grapefruit-medication interactions
Anti-anxiety; Buspirone (BuSpar)
Anti-arrhythmia; Amiodarone (Cordarone)
Antidepressant; Sertraline (Zoloft)
Antihistamine; Fexofenadine (Allegra)
Anti-retroviral Saquinavir; (Invirase), indinavir (Crixivan)
Anti-seizure Carbamazepine; (Carbatrol, Tegretol)
Calcium channel blocker; Nifedipine (Procardia), nimodipine (Nimotop), nisoldipine (Sular)
Immunosuppressant; Cyclosporine (Neoral, Sandimmune), tacrolimus (Prograf), sirolimus (Rapamune)
Statin; Simvastatin (Zocor), lovastatin (Mevacor), atorvastatin (Lipitor)

Covered in the December 2010 online issue of "Today's Dietitian" is a comprehensive article on food and medication interactions, entitled; "When Foods and Drugs Collide — Studies Expose Interactions Between Certain Foods and Medications."written by Denise Webb, PhD, RD .

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