.
Combination drug: Tarka®
Verapamil is one of the calcium channel blocker drugs used to treat angina pectoris, heart arrhythmias, and high blood pressure (hypertension).
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.
Summary of Interactions for Verapamil
| Depletion or interference | None known |
|---|---|
| Adverse interaction | Calcium (for
people with high blood pressure) Pleurisy root* Vitamin D* |
| Side effect reduction/prevention | Calcium (for
people with high blood pressure) Fiber Fluid |
| Supportive interaction | None known |
| Reduced drug absorption/bioavailability | None known |
| Other (see text) | Grapefruit juice |
For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
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 VitaminLore 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.