Levodopa, phenobarb, phenytoin, cycloserine, hydralazine, penicillamine, cyclosporin. Reduced vit B
12 absorption by co-administration of aminoglycoside, colchicines, prolonged-release K-based products, aminosalicylic acid, anticonvulsants, cobalt, alcohol & ascorbic acid. Prednisone. Chloramphenicol. Plasma elevations of lithium-based products, digoxin, MTX & NSAIDs.