Chronic excessive consumption of vit A. Patient w/ renal failure, erythrocyte G6PD deficiency, hemochromatosis, sickle cell anemia & thalassemia. High doses of vit E (>100 IU); lesions w/ tendency to bleed; history of hemorrhagic stroke & bleeding disorders. Kidney disease. Concomitant use w/ other supplements, herbal or other caffeine-containing products.
Increased bleeding may occur w/ large doses of vit A w/ anticoagulant (eg, warfarin). Decreased anticoagulant effect of warfarin w/ vit C. Vit E may have anti-vit K effects. Concomitant intake of anticoagulants may result in hemorrhage. Decreased absorption of cephalosporins, quinolones & tetracyclines w/ Zn. Concomitant administration w/ Zn inhibits absorption of Cu & Fe. Increased urinary excretion of ascorbic acid & decreased excretion w/ aspirin. Prolonged statin treatment may increase vit A levels. Neomycin, aminosalicylic acid, colchicine, cimetidine slows down absorption of some vit.
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