Vitamin D - Diltiazem Interaction

Interaction Details

Diltiazem is classified as belonging to the following category: Cytochrome P450 3A4 (Cyp3A4) Substrates

Vitamin D might induce CYP3A4 enzymes and reduce the bioavailability of CYP3A4 substrates.
There is some concern that vitamin D might induce CYP3A4. In vitro research suggests that vitamin D induces CYP3A4 transcription. Additionally, observational research has found that increased UV light exposure and serum vitamin D levels are associated with decreased serum levels of CYP3A4 substrates such as tacrolimus and sirolimus, while no association between UV light exposure or vitamin D levels and levels of mycophenolic acid, a non-CYP3A4 substrate, was found. A small, low-quality clinical study shows that taking vitamin D reduces levels of the CYP3A4 substrate atorvastatin and its active metabolites by up to 55%; however, the clinical effects of atorvastatin were not reduced. While researchers theorized that vitamin D might induce CYP3A4, this proposed mechanism was not specifically studied.

Interaction Rating

Likelihood of Occurrence

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists

References

• Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: A new drug interaction with an unexpected consequence. Clin Pharmacol Ther 2009;85:198-203.
• Wang Z, Schuetz EG, Xu Y, Thummel KE. Interplay between vitamin D and the drug metabolizing enzyme CYP3A4. J Steroid Biochem Mol Biol 2013;136:54-8.

Interaction Details

Diltiazem is classified as belonging to the following category: Diltiazem (Cardizem, Others)

Theoretically, hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of diltiazem for arrhythmia.
High doses of vitamin D can cause hypercalcemia. Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically this could also occur with diltiazem. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and diltiazem concurrently.

Interaction Rating

Likelihood of Occurrence

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.

References

• Bar-Or D, Yoel G. Calcium and calciferol antagonize effect of verapamil in atrial fibrillation. Br Med J 1981;282:1585-6.

Diltiazem Overview

• Diltiazem is used to treat high blood pressure and to control angina (chest pain). Diltiazem is in a class of medications called calcium-channel blockers. It works by relaxing the blood vessels so the heart does not have to pump as hard. It also increases the supply of blood and oxygen to the heart.

• High blood pressure is a common condition, and when not treated it can cause damage to the brain, heart, blood vessels, kidneys, and other parts of the body. Damage to these organs may cause heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision, and other problems. In addition to taking medication, making lifestyle changes will also help to control your blood pressure. These changes include eating a diet that is low in fat and salt, maintaining a healthy weight, exercising at least 30 minutes most days, not smoking, and using alcohol in moderation.

Vitamin D - More Interactions

Vitamin D interacts with 694 drugs

Interaction Rating Key

These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.