Vitamin D and Medications

Your body needs vitamin D to function. However, certain medications can interact poorly with vitamin D. Sometimes, these medications result in a vitamin deficiency. In other cases, the drugs you take could lead to an excess of vitamin D in your body, which can also cause problems.

What is vitamin D, and how might it interact with certain medications? Vitamin D is a fat-soluble vitamin that helps your body absorb calcium. It also plays a role in cell growth and immune system health. In most cases, your body can regulate how much vitamin D it needs. But if you take vitamin D supplements, you may end up with an excess of vitamin D in your body. In addition, certain medicines can lead to low vitamin D levels or problems with vitamin D absorption.

What Medications Might Lead to Low Vitamin D?

There are a number of medications and supplements that can reduce vitamin D levels, make it more difficult for your body to absorb vitamin D, or increase vitamin D metabolism. These include certain anti-seizure drugs and stimulant laxatives, as well as:

• Cholestyramine (also known as Questrann, LoCholest and Prevalite)
• Colestipol
• Mineral oil
• Orlistat (also known as Xenical or alli)
• Phenobarbital
• Phenytoin (also known as Dilantin)Rifampin.

In addition, older adults who take corticosteroids (such as prednisone) for chronic obstructive pulmonary disease (COPD), asthma, lupus and other conditions may be more likely to develop osteoporosis, or brittle bones, especially if they have been taking the medications for a long time. This is because corticosteroids reduce calcium absorption and inhibit metabolism of vitamin D. There is some evidence that vitamin D supplements might help improve bone strength for these individuals.

What Medications Does Vitamin D Interact With?

Vitamin D also interacts with a number of medications and other substances, including:

• Aluminum: Aluminum is found in many antacids. Vitamin D can increase the amount of aluminum your body absorbs, which might cause problems for people with kidney disease.
• Calcipotriene (also known as Dovonex): You should avoid vitamin D supplements if you are taking this drug, since calcipotriene and vitamin D have similar chemical makeups. Taking them together can increase the side effects of calcipotriene.
• Digoxin (also known as Lanoxin): Combining vitamin D with digoxin (which helps your heart beat stronger) might cause an irregular heartbeat.
• Diltiazem (also known as Cardizem, Dilacor and Tiazac): Large quantities of vitamin D taken in combination with diltiazem might make the medication less effective.

• Verapamil (also known as Calan, Covera, Isoptin and Verelan): You should not take large quantities of vitamin D if you are taking verapamil.

• Water pills (also known as Thiazide diuretics): Combining large quantities of vitamin D with water pills could result in a build-up of calcium in your body. Too much calcium in your body might lead to kidney problems.
  
  Always be sure to tell your doctor about all the medications and vitamin supplements you are taking to avoid potentially dangerous side effects.

Resources

Mayo Clinic Staff. (2008). Prednisone and other corticosteroids: Balance the risks and benefits. Retrieved December 18, 2009, from the Mayo Clinic website: http://www.mayoclinic.com/health/steroids/HQ01431

MedlinePlus Staff. (2009). Vitamin D. Retrieved December 18, 2009, from the MedlinePlus website: http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-vitamind.html#Interactions

National Heart, Lung and Blood Institute Staff. (n.d.). How is asthma treated and controlled. Retrieved December 18, 2009, from the National Heart, Lung and Blood Institute website: http://www.nhlbi.nih.gov/health/dci/Diseases/Asthma/Asthma_Treatments.html

National Institutes of Health, Office of Dietary Supplements Staff. (2009). Dietary Supplement Fact Sheet: Vitamin D. Retrieved December 18, 2009, from the National Institutes of Health website: http://ods.od.nih.gov/factsheets/vitamind.asp