osteoporosis
11 interactions related to osteoporosis
prednisone + vitamin d
Glucocorticoids accelerate the catabolism of 25-hydroxyvitamin D, lower active vitamin D metabolites at the gut, and impair calcium absorption. Population data show oral steroid users have more than double the rate of severe vitamin D deficiency compared to non-users.
amlodipine + calcium
Theoretically, high doses of supplemental calcium could blunt the vasodilatory effect of calcium channel blockers such as amlodipine, but controlled human data are limited. Drugs.com flags this as a minor monitor-only interaction with weak clinical evidence.
risedronate + calcium
Calcium and other divalent cations bind risedronate in the gut and form insoluble complexes, blocking absorption of a drug whose oral bioavailability is already very low (~0.6%). Co-administration can reduce the dose to subtherapeutic levels.
alendronate + coffee
Studies cited in the FDA label show coffee (and orange juice) reduce alendronate bioavailability by approximately 60%. Given the drug's already minuscule baseline absorption of ~0.6%, this drop can render the dose therapeutically ineffective.
prednisone + calcium
Glucocorticoids like prednisone impair intestinal calcium absorption and increase urinary calcium loss, contributing to negative calcium balance and accelerated bone loss. This is a depletion-and-displacement effect, not a chemical interaction in the gut.
calcium + magnesium
Calcium and magnesium work together in bone mineralization, muscle contraction, and nerve signaling, but they compete for absorption through the same intestinal transporters at high single doses. Maintaining a dietary calcium-to-magnesium intake ratio in the 2:1 to 3:1 range is associated with the highest bone mineral density and lowest osteoporosis risk.
boron + calcium
Boron reduces urinary calcium excretion and supports the hydroxylation of vitamin D into its active form, which in turn enhances intestinal calcium absorption. Postmenopausal women taking 3 mg/day of boron have shown reduced urinary calcium loss and improved markers of calcium retention.
alendronate + calcium
Calcium binds alendronate in the gut and forms an insoluble chelate, drastically reducing absorption of an already poorly bioavailable bisphosphonate (oral bioavailability is only ~0.6%). Co-administration can render the osteoporosis drug clinically ineffective.
methylprednisolone + vitamin d
Methylprednisolone, like other glucocorticoids, is associated with increased catabolism of 25-hydroxyvitamin D and impaired vitamin D-mediated intestinal calcium absorption. Long-term use contributes to vitamin D deficiency and accelerated bone loss.
raloxifene + st. john's wort
Although raloxifene is cleared primarily by glucuronidation rather than CYP3A4, St. John's Wort induces P-glycoprotein and other transporters that may reduce raloxifene exposure. Drug interaction databases list a documented reduction in raloxifene serum concentration with concurrent use, potentially undermining osteoporosis treatment.
caffeine + vitamin d
In vitro and observational studies suggest high caffeine intake (>300 mg/day) may decrease vitamin D receptor (VDR) protein expression in osteoblasts and is associated with lower serum 25-hydroxyvitamin D levels in some NHANES data. The clinical effect is modest and most relevant for bone health in postmenopausal women with low calcium intake.