Juice may seem like a harmless food, but drinking certain types of it with certain medications can have ill effects. For example, drinking grapefruit juice with certain medications alters the metabolism of some drugs, dangerously increasing blood levels. Researchers are still investigating to see if cranberry juice has a similar impact on drug metabolism. So talk to your doctor before downing your next dose with a glass of cranberry juice.
Cranberry Juice
Cranberry juice is a nutrient-rich juice recommended as a beverage to help prevent urinary tract infections. It may also help lower blood cholesterol levels, according to a 2003 report from "Science Daily." A 1-cup serving of unsweetened cranberry juice contains 116 calories, 1 g of protein, 0 g of fat, 30 g of carbohydrates, 20 mg of calcium, 195 mg of potassium, 24 mg of vitamin C, 114 IU of vitamin A, and 3 mg of vitamin E.
Cranberry Juice and Drug Metabolism
Concern over cranberry juice started after several case reports, both in the United States and the United Kingdom, showed possible interactions between cranberry juice and the blood thinner warfarin. Cranberry juice may inhibit the enzyme that metabolizes warfarin, altering its blood-thinning capabilities. The case reports indicate that the cranberry juice increased the effectiveness of warfarin, causing blood to become too thin and increasing bleeding risk. Because cranberry juice inhibits an enzyme like grapefruit juice, it may also alter the metabolism of other medications.
Warfarin
Given the case reports, research was conducted to evaluate if cranberry juice altered the metabolism of warfarin. A 2007 study published in "Clinical Pharmacology and Therapeutics" investigated the effects of cranberry juice on the metabolism of warfarin, tizanidine, and midazolam. Ten healthy volunteers drank 200 ml of cranberry juice or water for 10 days. On the fifth day, the volunteers were given a dose of warfarin, tizanidine, and midazolam. The researchers did not see an increase in blood plasma levels of the medication or an increase in the effectiveness of the warfarin in the group given the cranberry juice. A 2007 review study published in the "American Journal of Health-System Pharmacy" reviewed two clinical trials, along with the case reports and concluded that while there is no evidence that cranberry juice increases the effectiveness of warfarin, more research is necessary.
Considerations
Diclofenac is also metabolized by an enzyme that may be inhibited by cranberry juice. Diclofenac is a non-steroidal anti-inflammatory drug used to treat pain caused by arthritis or ankylosing spondylitis. A 2009 clinical trial published in the "British Journal of Pharmacology" investigated the effects of cranberry juice on the metabolism of diclofenac in a group of healthy volunteers. While cranberry juice decreased the metabolism of diclofenac in human liver samples, researchers found that the cranberry juice did not decrease the medication's effectiveness in human subjects.
References
- Science Daily; Study Provides New Evidence That Cranberry Juice May Help Fight Heart Disease; March 2003
- The University of North Carolina at Chapel Hill: Faculty Spotlight: Mary Paine, PhD, RPh
- "British Journal of Clinical Pharmacology"; Cranberry Juice Suppressed the Diclofenac Metabolism by Human Liver Microsomes, But Not in Healthy Human Subjects; K. Ushijima, et al.; August 2009
- "Clinical Pharmacology and Therapeutics"; Effects of Daily Ingestion of Cranberry Juice on the Pharmacokinetics of Warfarin, Tizanidine, and Midazolam--Probes of CYP2C9, CYP1A2, and CYP3A4; J.J. Lilja; June 2007
- "American Journal of Health-System Pharmacy"; Interaction Potential Between Cranberry Juice and Warfarin; March 2007
- USDA; Nutrient Database; Cranberry Juice, Unsweetened
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