Niacinamide: May decrease carbamazepine clearance. Pyridoxine HCl (vit B
6): Reversed effects of l-dopa. Decrease serum level of phenobarb & phenytoin. May enhance amiodarone-induced photosensitivity reactions. Na ascorbate (vit C): Increased risk of Al toxicity w/ antacids. Increased urinary excretion of ascorbic acid & decreased excretion of aspirin. May interfere w/ alcohol-disulfiram reaction. Decreases plasma level of fluphenazine. May accelerate excretion of mexiletine. Increases apparent t
1/2 w/ paracetamol. Reduced blood levels w/ OCs (containing estrogens). Decreased anticoagulant effect of warfarin. D-α-tocopheryl acid succinate (vit E): May result in hemorrhage w/ anticoagulants. May potentiate effects of antiplatelets (eg, aspirin, clopidogrel, ticlopidine) & herbs w/ antithrombotic activity (eg, garlic & ginkgo). Lowered plasma levels w/ anticonvulsants (eg, phenobarb, phenytoin, carbamazepine) & OCs. May decrease/impair absorption w/ cholestyramine, colestipol, INH, mineral oil, neomycin, orlistat, or sucralfate. May reduce the requirement for digoxin & insulin. May decrease antioxidative effect of a supplement containing vit E. Enhanced side effects of some drugs (eg, amiodarone, ciclosporin, & zidovudine). Zn: Decreased absorption w/ quinolone antibiotics (eg, ciprofloxacin, levofloxacin, ofloxacin) & tetracyclines (eg, doxycycline). Decreased absorption w/ bisphosphonates (eg, alendronate, etidronate, risedronate). Additive effects w/ cholesterol medicines. Inhibits absorption w/ Cu & Fe. Reduce absorption of penicillamine. Reduced absorption w/ caffeine or tea, high levels of P, Ca (dairy), phytates (eg, bran, brown bread), or folic acid.