Ascorbic acid (vit C): Enhanced tissue Fe toxicity of desferrioxamine. Enhanced absorption of Fe. Reduced cyclosporine blood level. May interfere w/ effectiveness of indinavir & warfarin. May interfere w/ testing kits & meters that measure glucose levels resulting in false readings. Cholecalciferol (vit D
3): Reduced urinary excretion of Ca w/ thiazide diuretics. Decreased GI absorption w/ orlistat, Fe exchange resins (eg, cholestyramine), laxatives (eg, mineral oil, senna). Increased risk of hypervitaminosis D &/or hypercalcaemia w/ vit D analogues (eg, ergocalciferol, calcitriol, & topical calcipotriene). Zn: Forms complexes w/ tetracyclines, quinolones, penicillamine, bisphosphonates, levothyroxine, eltrombopag resulting in decreased absorption of both substances.