with Vitamin D|
Antacids that bind phosphate may alter the levels, metabolism, and
availability of vitamin D. There is a case report of osteomalacia in a patient
that consumed large amounts of antacids (Godsall et al. 1984).
Aluminum-containing antacids may also increase the risk of fractures from
osteomalacia resistant to the administration of vitamin D; this is of particular
concern for people at risk for aluminum toxicity including newborns, elderly,
and people with kidney or liver disease (Henning
The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3),
interacted synergistically with doxorubicin by increasing the cytotoxic activity
of the drug against breast cancer cells in vitro (Ravid et al. 1999).
In one study, both total and free 1,25-(OH)2D concentrations increased in
women within 5 years of menopause who were being treated with unopposed estrogen
for three cycles (Bikle et al. 1992). With the addition of progestin, the levels
of vitamin D returned toward baseline. Progestin may antagonize some of the
beneficial effects of estrogen on calcium balance and bone metabolism; it is not
clear if vitamin D supplementation will overcome this effect.
Thiazide diuretics enhance the biological activity of vitamin D and increase
the risk of hypercalcemia (Hines Burnham et al 2000).
Verapamil may induce parathyroid hormone (PTH) resistance accompanied by a
decrease in 1,25(OH)D3 levels (Fox 1988). Studies in rats have demonstrated that
the negative correlation between PTH and vitamin D levels is significant.
However, this interaction does not appear to have long-term effects on calcium
homeostasis because of a dose-dependent increase in duodenal absorption of
Bikle DD, Halloran BP, Harris ST, Portale AA. Progestin antagonism of
estrogen stimulated 1,25-dihydroxyvitamin D levels. J Clin Endocrinol
Fox J. Verapamil induces PTH resistance but increases duodenal calcium
absorption in rats. Am J Physiol. 1988;255(5):E702-707.
Godsall JW, Baron R, Insogna KL. Vitamin D metabolism and bone
histomorphometry in a patient with antacid-induced osteomalacia. Am J
Henning HV. Aluminum toxicity [in German]. Klin Wochenschr.
Hines Burnham, et al, eds. Drug Facts and Comparisons. St. Louis,
MO:Facts and Comparisons; 2000:9.
Ravid A, Rocker D, Machlenkin A, et al. 1,25-Dihydroxyvitamin D3 enhances the
susceptibility of breast cancer cells to doxorubicin-induced oxidative damage.
Cancer Res. 1999;59:862-867.
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