Also indexed as: Calan, Covera-HS, Isoptin, Verelan
Summary of
Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem
contradictory. For clarification, read the full article for details about the summarized
interactions.
 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)
Pleurisy root*
Vitamin D*
|
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
|
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 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.