Vitamin D (efficacy, interactions and dosage)

Vitamin D

 Cautionary use

Vitamin D is LIKELY SAFE when taken by mouth in recommended amounts. Most people do not commonly experience side effects with vitamin D, unless too much is taken. Some side effects of taking too much vitamin D include weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, vomiting, and others.
Taking vitamin D for long periods of time in doses higher than 4000 units per day is POSSIBLY UNSAFE and may cause excessively high levels of calcium in the blood. However, much higher doses are often needed for the short-term treatment of vitamin D deficiency. This type of treatment should be done under the supervision of a healthcare provider.

Special precautions & warnings:

Pregnancy and breast-feeding: Vitamin D is LIKELY SAFE during pregnancy and breast-feeding when used in daily amounts below 4000 units. Do not use higher doses. Using higher doses might cause serious harm to the infant.

Kidney disease: Vitamin D may increase calcium levels and increase the risk of “hardening of the arteries” in people with serious kidney disease. This must be balanced with the need to prevent renal osteodystrophy, a bone disease that occurs when the kidneys fail to maintain the proper levels of calcium and phosphorus in the blood. Calcium levels should be monitored carefully in people with kidney disease.

High levels of calcium in the blood: Taking vitamin D could make this condition worse.

“Hardening of the arteries” (atherosclerosis): Taking vitamin D could make this condition worse.

Sarcoidosis: Vitamin D may increase calcium levels in people with sarcoidosis. This could lead to kidney stones and other problems. Use vitamin D cautiously.

Histoplasmosis: Vitamin D may increase calcium levels in people with histoplasmosis. This could lead to kidney stones and other problems. Use vitamin D cautiously.

Over-active parathyroid gland (hyperparathyroidism): Vitamin D may increase calcium levels in people with hyperparathyroidism. Use vitamin D cautiously.

Lymphoma: Vitamin D may increase calcium levels in people with lymphoma. This could lead to kidney stones and other problems. Use vitamin D cautiously.

Interactions with medications

Moderate

Be cautious with this combination.

Aluminum

Aluminum is found in most antacids. Vitamin D can increase how much aluminum the body absorbs. This interaction might be a problem for people with kidney disease. Take vitamin D two hours before, or four hours after antacids.

Atorvastatin (Lipitor)

Vitamin D might decrease the amount of atorvastatin (Lipitor) that enters the body. This might decrease how well atorvastatin (Lipitor) works.

Calcipotriene (Dovonex)

Calcipotriene is a drug that is similar to vitamin D. Taking vitamin D along with calcipotriene (Dovonex) might increase the effects and side effects of calcipotriene (Dovonex). Avoid taking vitamin D supplements if you are taking calcipotriene (Dovonex).

Digoxin (Lanoxin)

Vitamin D helps your body absorb calcium. Calcium can affect the heart. Digoxin (Lanoxin) is used to help your heart beat stronger. Taking vitamin D along with digoxin (Lanoxin) might increase the effects of digoxin (Lanoxin) and lead to an irregular heartbeat. If you are taking digoxin (Lanoxin), talk to your doctor before taking vitamin D supplements.

Diltiazem (Cardizem, Dilacor, Tiazac)

Vitamin D helps your body absorb calcium. Calcium can affect your heart. Diltiazem (Cardizem, Dilacor, Tiazac) can also affect your heart. Taking large amounts of vitamin D along with diltiazem (Cardizem, Dilacor, Tiazac) might decrease the effectiveness of diltiazem.

Medications changed by the liver (Cytochrome P450 3A4 (CYP 3A4) substrates)

Some medications are changed and broken down by the liver. Vitamin D may increase how quickly the liver breaks down some medications. Taking vitamin D along with some medications may decrease the effectiveness of some medications. Before taking vitamin D, talk to your health care provider if you are taking any medications that are changed by the liver.

Some of these medications changed by the liver include lovastatin (Mevacor), clarithromycin (Biaxin), cyclosporine (Neoral, Sandimmune), diltiazem (Cardizem), estrogens, indinavir (Crixivan), triazolam (Halcion), and others.

Verapamil (Calan, Covera, Isoptin, Verelan)

Vitamin D helps your body absorb calcium. Calcium can affect the heart. Verapamil (Calan, Covera, Isoptin, Verelan) can also affect the heart. Do not take large amounts of vitamin D if you are taking verapamil (Calan, Covera, Isoptin, Verelan).

Water pills (Thiazide diuretics)

Vitamin D helps your body absorb calcium. Some “water pills” increase the amount of calcium in the body. Taking large amounts of vitamin D along with some “water pills” might cause to be too much calcium in the body. This could cause serious side effects including kidney problems.

Some of these “water pills” include chlorothiazide (Diuril), hydrochlorothiazide (HydroDIURIL, Esidrix), indapamide (Lozol), metolazone (Zaroxolyn), and chlorthalidone (Hygroton).

Minor

Be watchful with this combination.

Cimetidine (Tagamet)

The body changes vitamin D into a form that it can use. Cimetidine (Tagamet) might decrease how well the body changes vitamin D. This might decrease how well vitamin D works. But this interaction probably isn’t important for most people.

Heparin

Heparin slows blood clotting and can increase the risk of breaking a bone when used for a long period of time. People taking these medications should eat a diet rich in calcium and vitamin D.

Low molecular weight heparins (LMWHs)

Some medications called low molecular weight heparins can increase the risk of breaking a bone when used for a long periods of time. People taking these medications should eat a diet rich in calcium and vitamin D.

These drugs include enoxaparin (Lovenox), dalteparin (Fragmin), and tinzaparin (Innohep).

Interactions with herbs and supplements

Magnesium

Taking vitamin D can raise the level of magnesium in people who have low magnesium and low vitamin D levels. In people with normal magnesium levels, this doesn’t seem to happen.

Interactions with foods

There are no known interactions with foods.

Recommended dose

The following doses have been studied in scientific research:

BY MOUTH:

  • For preventing osteoporosis and fractures: 400-1000 IU per day has been used for older adults. Some experts recommended higher doses of 1000-2000 IU daily.
  • For preventing falls: 800-1000 IU/day has been used in combination with calcium 1000-1200 mg/day.
  • For preventing multiple sclerosis (MS): long-term consumption of at least 400 IU per day, mainly in the form of a multivitamin supplement, has been used.
  • For preventing all cancer types: calcium 1400-1500 mg/day plus vitamin D3 (cholecalciferol) 1100 IU/day in postmenopausal women has been used.
  • For muscle pain caused by medications called “statins”: vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol) 50,000 units once a week or 400 IU daily.
  • For preventing the flu: vitamin D (cholecalciferol) 1200 IU daily.

Most vitamin supplements contain only 400 IU (10 mcg) vitamin D.

The Institute of Medicine publishes recommended daily allowance (RDA), which is an estimate of the amount of vitamin D that meets the needs of most people in the population. The current RDA was set in 2010. The RDA varies based on age as follows: 1-70 years of age, 600 IU daily; 71 years and older, 800 IU daily; pregnant and lactating women, 600 IU daily. For infants ages 0-12 months, an adequate intake (AI) level of 400 IU is recommended.

Some organizations are recommending higher amounts. In 2008, the American Academy of Pediatrics increased the recommended minimum daily intake of vitamin D to 400 IU daily for all infants and children, including adolescents. Parents should not use vitamin D liquids dosed as 400 IU/drop. Giving one dropperful or mL by mistake can deliver 10,000 IU/day. The US Food and Drug Administration (FDA) will force companies to provide no more than 400 IU per dropperful in the future.

The National Osteoporosis Foundation recommends vitamin D 400 IU to 800 IU daily for adults under age 50, and 800 IU to 1000 IU daily for older adults.

The North American Menopause Society recommends 700 IU to 800 IU daily for women at risk of deficiency due to low sun (e.g., homebound, northern latitude) exposure.

Guidelines from the Osteoporosis Society of Canada recommend vitamin D 400 IU per day for people up to age 50, and 800 IU per day for people over 50. Osteoporosis Canada now recommends 400-1000 IU daily for adults under the age of 50 years and 800-2000 IU daily for adults over the age of 50 years.

The Canadian Cancer Society recommends 1000 IU/day during the fall and winter for adults in Canada. For those with a higher risk of having low vitamin D levels, this dose should be taken year round. This includes people who have dark skin, usually wear clothing that covers most of their skin, and people who are older or who don’t go outside often.

Many experts now recommend using vitamin D supplements containing cholecalciferol in order to meet these intake levels. This seems to be more potent than another form of vitamin D called ergocalciferol.

References:

Posted in Pharmacy

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