Also listed as: Calciferol; Calcitrol;
If you are currently being treated with any of the following medications, you
should not use vitamin D supplements without first talking to your healthcare
Vitamin D levels may be increased by the following
Estrogen: Hormone replacement therapy with estrogen appears to
increase vitamin D levels in the blood; this may have a beneficial effect on
calcium and bone metabolism. In addition, use of vitamin D supplements in
conjunction with estrogen replacement therapy (ERT) increases bone mass more
than ERT alone. However, this benefit may be lost with the addition of
Isoniazid (INH): INH, a medication used to treat tuberculosis,
may raise blood levels of vitamin D.
Thiazide: Diuretics in this class (such as hydrochlorothiazide)
increase the activity of vitamin D and can lead to inappropriately high calcium
levels in the blood.
Vitamin D levels may be decreased, or its absorption may be reduced, by the
Antacids: Taking certain antacids for long periods of time may
alter the levels, metabolism, and availability of vitamin D.
Calcium-channel blockers (such as verapamil): These medications
are used to treat high blood pressure and heart conditions may decrease the
production of vitamin D by the body.
Cholestyramine: This cholesterol-lowering medication, known as
a bile acid sequestrant, interferes with the absorption of vitamin D (as well as
other fat soluble vitamins).
Phenobarbital, phenytoin, and other anticonvulsant medications:
These medications may accelerate the body's use of vitamin D.
Mineral oil also interferes with absorption.
In addition, Vitamin D may enhance the effects of doxorubicin, a
medicine used to treat a variety of cancers. More research is needed.
Some clinicians recommend following calcium levels closely if vitamin D is
taken with digoxin, a medication used to treat irregular heart rhythms.
This is because vitamin D improves absorption of calcium. Calcium, in turn, can
increase the likelihood of a toxic reaction from this medication.
Weight Loss Products Orlistat, a medication used for weight
loss and olestra, a substance added to certain food products, are both intended
to bind to fat and prevent the absorption of fat and the associated calories.
Because of their effects on fat, orlistat and olestra may also prevent the
absorption of fat-soluble vitamins such as vitamin D. Given this concern and
possibility, the Food and Drug Administration (FDA) now requires that vitamin D
and other fat soluble vitamins (namely, A, E, and K) be added to food products
containing olestra. How well vitamin D from such food products is absorbed and
used by the body is not clear. In addition, physicians who prescribe orlistat
add a multivitamin with fat soluble vitamins to the
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guide to self-medication. The reader is advised to discuss the information
provided here with a doctor, pharmacist, nurse, or other authorized healthcare
practitioner and to check product information (including package inserts)
regarding dosage, precautions, warnings, interactions, and contraindications
before administering any drug, herb, or supplement discussed