Verapamil

Safetychecker Summary for Verapamil
(for details about the summarized interactions, read the full article)

May be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication.	Calcium (for people with high blood pressure) Fiber Fluid
Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	Calcium (for people with high blood pressure) Vitamin D* Pleurisy root*
Check: Other—Before taking any of these supplements or eating any of these foods with your medication, read this article in full for details.	Grapefruit juice
Depletion or interference	None known
Supportive interaction	None known
Reduced drug absorption/bioavailability	None known

Interactions with Dietary Supplements

Calcium
Calcium supplementation has been reported to reverse the blood pressure-lowering actions of this drug when used to treat arrhythmias.¹ ² It remains unclear whether people taking verapamil for the purpose of lowering blood pressure should avoid calcium supplementation. These people should discuss the matter with the prescribing doctor.

On the other hand, people who take verapamil to treat other conditions, such as angina or heart arrhythmias, should discuss with their physicians the possibility of using low-level (as little as 27 mg per day) calcium supplementation, to reduce excessive blood pressure-lowering actions caused by verapamil in those who do not have high blood pressure.³

Vitamin D
Vitamin D may interfere with the effectiveness of verapamil.⁴ People taking verapamil should ask their doctor before using vitamin D-containing supplements.

Fluid and Fiber
Constipation is a common side effect of verapamil treatment.⁵ Increasing fluid and fiber intake can ease constipation.

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

Interactions with Foods and Other Compounds

Grapefruit juice
Grapefruit juice may increase verapamil blood levels.⁷ The importance of this interaction regarding verapamil effectiveness and side effects is unknown. Until more is known, it makes sense for people taking this drug to either avoid drinking grapefruit juice entirely or drink grapefruit juice only under the careful monitoring and supervision of the prescribing doctor. In theory, this last possibility might allow for a decrease in drug dose, but it could be dangerous in the absence of diligent monitoring. The same effects might be seen from eating grapefruit as from drinking its juice.

References:

1. Haft JI, Habbab MA. Treatment of atrial arrhythmias. Effectiveness of verapamil when preceded by calcium infusion. Arch Intern Med 1986;146:1085–9.

2. Weiss AT, Lewis BS, Halon DA, et al. The use of calcium with verapamil in the management of supraventricular tachyarrhythmias. Int J Cardiol 1983;4:275–80.

3. Kuhn M, Schriger DL. Low-dose calcium pretreatment to prevent verapamil-induced hypotension. Am Heart J 1992;124:231–2.

4. Threlkeld DS, ed. Diuretics and Cardiovasculars, Calcium Channel Blocking Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Nov 1992, 150–b.

5. Threlkeld DS, ed. Diuretics and Cardiovasculars, Calcium Channel Blocking Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Nov 1992, 150–b.

6. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press, 1996, 213–4.

7. Holt GA. Food & Drug Interactions. Chicago: Precept Press, 1998, 274–5.

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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 2003.