Felodipine

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Also indexed as:

Plendil

Felodipine is used to treat high blood pressure, Raynaud's syndrome, and congestive heart failure. It is in a class of drugs known as calcium channel blockers.

Herbs

Summary of Interactions for Felodipine

Depletion or interference	Calcium Magnesium Potassium
Adverse interaction	Grapefruit juice Pleurisy root* Pomegranate juice* Quercetin*
Side effect reduction/prevention	None known
Supportive interaction	None known
Reduced drug absorption/bioavailability	None known

An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

Interactions with Supplements

Potassium

Felodipine can lead to increased excretion of potassium.¹ A potassium deficiency may result if potassium intake is not sufficient. People taking felodipine should eat a high-potassium diet and be checked regularly for low blood potassium by a doctor.

Magnesium

Increased magnesium excretion has been observed in studies of individuals taking felodipine.² Therefore, some physicians may recommend magnesium supplementation to their patients taking felodipine.

Calcium

A study of felodipine indicated that the drug caused increased excretion of calcium.³ Whether this effect could lead to increased bone loss is unknown, but some health practitioners may recommend calcium supplementation to individuals taking felodipine. Although the effectiveness of some calcium channel blockers may be reduced with calcium supplementation,⁴ this effect has not been observed in people taking felodipine.

Quercetin

Quercetin is a flavonoid found in grapefruit juice, tea, onions, and other foods; it is also available as a nutritional supplement. Quercetin has been shown in test tube studies to inhibit enzymes responsible for breaking down felodipine into an inactive form.⁵ This interaction may result in increased blood levels of felodipine that could lead to unwanted side effects. Until more is known about this interaction, patients taking felodipine should avoid supplementing with quercetin.

Interactions with Herbs

Pleurisy root

As pleurisy root and other plants in the Aesclepius genus contain cardiac glycosides, it is best to avoid use of pleurisy root with heart medications such as calcium channel blockers.⁶

Other Interactions

Grapefruit

Regular consumption of grapefruit juice can increase the quantity of felodipine in the blood by reducing the breakdown of the drug.⁷ The inhibitory effect of grapefruit juice lasts up to 24 hours after ingestion and can increase blood levels nearly three times the expected amount. In order to prevent side effects of the drug, individuals who are taking felodipine should avoid grapefruit and its juice.

Pomegranate juice

Pomegranate juice has been shown to inhibit the same enzyme that is inhibited by grapefruit juice.^{8, 9} The degree of inhibition is about the same for each of these juices. Therefore, it would be reasonable to expect that pomegranate juice might interact with felodipine in the same way that grapefruit juice does.

Alcohol

Drinking alcoholic beverages while taking felodipine may enhance the blood pressure-lowering effect of the drug.¹⁰ Those who combine alcoholic beverages with felodipine should be aware of possible adverse consequences, such as increased lightheadedness.

References

1. Hulthen UL, Katzman PL. Renal effects of acute and long-term treatment with felodipine in essential hypertension. J Hypertens 1988;6:231-7.
2. Hulthen UL, Katzman PL. Renal effects of acute and long-term treatment with felodipine in essential hypertension. J Hypertens 1988;6:231-7.
3. Hulthen UL, Katzman PL. Renal effects of acute and long-term treatment with felodipine in essential hypertension. J Hypertens 1988;6:231-7.
4. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, Inc., 1997, 208.
5. Miniscalco A, Lundahl J, Regardh CG. Inhibition of dihydropyridine metabolism in rat and human liver microsomes by flavonoids found in grapefruit juice. J Pharmacol Exp Ther 1992;261:1195-9.
6. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press, 1996, 213-4.
7. Bailey DG, Malcolm J, Arnold O, Spence JD. Grapefruit juice-drug interactions. Br J Clin Pharmacol 1998;46:101-10.
8. Sorokin AV, Duncan B, Panetta R, Thompson PD. Rhabdomyolysis associated with pomegranate juice consumption. Am J Cardiol 2006;98:705-6.
9. Summers KM. Potential drug-food interactions with pomegranate juice. Ann Pharmacother 2006;40:1472-3.
10. Bailey DG, Spence JD, Edgar B, et al. Ethanol enhances the hemodynamic effects of felodipine. Clin Invest Med 1989;12:357-62.

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Last Review: 09-01-2007

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2008.

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