Alendronate Interactions

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.

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.