A study of felodipine indicated that the drug caused increased excretion of calcium.1 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,2 this effect has not been observed in people taking felodipine.
Increased magnesium excretion has been observed in studies of individuals taking felodipine.3 Therefore, some physicians may recommend magnesium supplementation to their patients taking felodipine.
Felodipine can lead to increased excretion of potassium.4 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.
Regular consumption of grapefruit juice can increase the quantity of felodipine in the blood by reducing the breakdown of the drug.5 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 has been shown to inhibit the same enzyme that is inhibited by grapefruit juice.6 , 7 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.
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.8 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.
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.9
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. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, Inc., 1997, 208.
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. Hulthen UL, Katzman PL. Renal effects of acute and long-term treatment with felodipine in essential hypertension. J Hypertens 1988;6:231–7.
5. Bailey DG, Malcolm J, Arnold O, Spence JD. Grapefruit juice-drug interactions. Br J Clin Pharmacol 1998;46:101–10.
6. Sorokin AV, Duncan B, Panetta R, Thompson PD. Rhabdomyolysis associated with pomegranate juice consumption. Am J Cardiol 2006;98:705–6.
7. Summers KM. Potential drug-food interactions with pomegranate juice. Ann Pharmacother 2006;40:1472–3.
8. 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.
9. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press, 1996, 213–4.
Last Review: 11-07-2012
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